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V 



FIRST PRINCIPLES 



C HE M I S TRY, 




FOE THE USE OF 



-J. 

COLLEGES AND SCHOOLS 



BY BENJAMIN SILLIMAN, Jr., M. A. 

PROFESSOR IN YALE COLLEGE OB" CHEMISTRY AS APPLIED TO THE ARTS 



WITH MORE THAN TWO HUNDRED ILLUSTRATIONS. 



TENTH THOUSAND. 



PHILADELPHIA: 
PUBLISHED BY HORACE C. PECK 

NEW-HAVEN : DURR1E & PECK. 
1849. 



cm 3o 



Entered according to Act of Congress, in the year 1846, by 

LOOMIS & PECK, 
in the Clerk's Office of the District Court of Connecticut. 



E. B. MEARS, STEREOTYPES, 

Hart's Building?, N. E. corner 01 Sixth and Chesnut. 

SMITH AND PETERS, PRINTERS, 

Franklin Buildings, Sixth street below Arch, Philadelphia. 



TO 

PROFESSOR SILLIMAN, 

THIS VOLUME, 

DESIGNED 

TO PROMOTE THE CAUSE OF SCIENCE, 

TO WHICH HE HAS DEVOTED HIS LIFE, 

18 RESPECTFULLY DEDICATED, 

BY HI3 SON, 

THE AUTHOR. 



PREFACE TO THE SECOND EDITION. 

The sale of the first edition of three thousand copies of this work 
in the space of a few months, has required the preparation of a new 
edition at an earlier date than was originally anticipated. Every 
part of the book has been thoroughly revised and corrected, and 
some portions have been entirely rewritten. At the same time, 
the author has desired to avoid the common error of making unim- 
portant changes, which serve only to annoy teachers who already 
use the book. 

The Organic Chemistry has been entirely rewritten (with the 
exception of the last twenty pages), by the same able hand that 
prepared it in the first edition. It is believed that this change will 
give great satisfaction to all who are not tied by prejudice to the 
theory of organic radicals — those ideal creations, which, with the 
appearance of simplicity, really encumber us with a load of unreal 
knowledge. The simpler and more truthful philosophy of the new 
French school, which is now for the first time presented in an ele- 
mentary form, will, it is believed, be soon generally adopted. 

The adoption of this work by many of the first seminaries of 
learning in this country, is a gratifying evidence to the author that 
his design has been appreciated ; and he trusts that those who gave 
their confidence to the first edition, will find the present one, in 
some important respects, superior to it. 

As the work is now stereotyped, it must remain in its present 
form until the progress of the science requires it to be again re- 
modeled. 

Yale College, New Haven, Ct. ) 

Analytical Laboratory, Sept. 15, 1847. > 



FROM THE PREFACE TO THE FIRST EDITION. 

The object of this work is sufficiently indicated by its title. It 
has grown out of the exigencies of teaching, and has been received 
as the Text Book in the public lectures at Yale College. 

It is important that a work of this kind should contain only such 
matter as is actually taught to a class by recitations and lectures. 
1* 



VI PREFACE. 

All fulness beyond this is unavailable to either teacher or pupil, 
and serves often to embarrass the one and to discourage the other. 
This is perhaps the reason why several works, otherwise excellent, 
have failed to answer the purpose for which they were written. 
The science of Chemistry has now reached the point where its 
First Principles can be presented by the teacher with almost mathe- 
matical precision. 

Chemistry has attractions of an economical and experimental 
character, which will always secure for it a place in every system 
of education. Without wishing to diminish its claims to attention 
on these grounds, the author urges the paramount advantages pos- 
sessed by his favorite science, as a study peculiarly fitted to train 
the mind to a methodized and logical habit of thought. If nothing 
more is to be derived from its study than the entertainment offered 
by brilliant phenomena, and a knowledge of convenient economical 
processes, the pupil will fail of its most important advantage. The 
beautiful philosophy, the perspicuous nomenclature, and lucid 
method of modern chemistry, are so obvious that they cannot fail 
to awaken the attention of every intelligent pupil, and carry him 
on his course of intellectual culture with rapid progress. * * * * 

The author has consulted all the best authorities within his reach, 
both in the standard systems of England and France, and in the 
scientific journals of this country and Europe. The works of Dan- 
iell, Graham, Brande, Kane, Fownes, Gregory, Faraday, Mitscher- 
lich, Berzelius, Dumas, Liebig, and Gerhardt, have all been used, as 
also the treatises of Dr. Hare and Prof. Silliman. 

The Organic Chemistry is presented mainly in the order of Lie- 
big in his Traiti de Chimie Organique. The author takes pleasure 
in acknowledging the important aid derived in this portion of the 
work from his friend and professional assistant, Mr. Thomas S. 
Hunt, whose familiarity with the philosophy and details of Chem- 
istry, will not fail to make him one of its ablest followers. The 
labor of compiling the Organic Chemistry has fallen almost solely 
upon him. ****♦*•*»* 

If it shall be found to meet the wants of both teachers and pupils, 
and to promote the progress of Scientific Chemistry in this coun 
try, the author will feel that he has not labored in vain. 

New Haven, December 1, 1846. 






TABLE OF CONTENTS. 



PART I. 



PHYSICS. 



PAGE 

Introduction, . . 13 

Sources of Knowledge, 13 
Distinction between the an- 
cient and modern philo- 
sophy, ... 14 
Physical and Intellectual 

Philosophy, . . 14 
General divisions of our 
knowledge of nature, 15 
Matter. — General Properties 

of Matter, . . 16 
Molecules, or Atoms, 17 

Indestructibility of Matter, 

and Cohesion, . . 18 
Repulsion and Chemical 

Attraction, . . 19 
Elements and Impondera- 
ble Agents, . . 20 
" The Three States of Mat- 
ter—the Solid, the Flu- 
id, and the Gaseous, 21 
The Atmosphere and Laws 

of Gases, . . 24 

Air-Pump, . . 26 

Law of Mariotte, . 27 
Barometer, . . 29 

Limits of the Atmosphere, 32 
Weight and Specific Gra- 
vity, ... 33 
Standards of Specific Gra- 
vity, ... 34 
Specific Gravity of Liquids, 35 



PAGE 

Specific Gravity of Solids, 36 

The Hydrometer, . 39 

Specific Gravity of Gases, 41 

Light, Sources and Nature, 41 

Reflection, ... 43 

Refraction, . . 44 

Prism and Analysis of 

Light, ... 46 
Double Refraction, . 48 
Polarization, . . 49 
Chemical Rays, . . 50 
Spectral Impressions, . 51 
Phosphorescence, . 52 
Heat — Sources, . . 53 
Expansion, . . 55 
Thermometers, . . 56 
Pyrometers, . . 62 
Laws of Expansion, . 63 
Unequal Expansion of Wa- 
ter, ... 65 
Communication of Heat, 67 
Conduction, . . 68 
Convection of Heat, . 71 
Radiant Heat, . . 72 
Absorption, . . 73 
Transmission of Heat, 74 
Melloni's Experiments, 75 
Specific Heat or Capacity, 78 
Changes produced by Heat 
in the State of Bodies, 
Liquefaction, . . 79 
Freezing and Melting, 81, 82 



V 1 



CONTENTS. 



Vaporization, (Boiling- 

Points,) ... 83 
Cryophorus, . . 87 
Elevation of Boiling-Points 

by Pressure, . . 88 
The Steam Engine, . 90 
Evaporation, . . 90 
Maximum Density of Va- 
pors, ... 91 
Diffusion of Gases, . 92 
Dew Point, . . 93 

Hygrometers, . . 94 
Spheroidal State of Bodies, 95 
Liquefaction of Gases, 95, 96 
Electricity. — Of Magnetism, 98 
Magnetics and Diamag- 

netics, . . .102 
Electricity of Friction, 103 
Theories of Electricity, 105 



PAGE 

Electroscopes, . . 106 
Electrical Machines, . 107 
Leyden Jar and Electro- 

phorous, . . 108 

Electricity of Chemical 

Action — Galvanism, 109 
Voltaic Pile, . . Ill 
Simple Voltaic Circle, 112 
Compound Voltaic Circle, 113 
Galvanic Batteries, . 115 
Electro-Magnetism, . 116 
Ampere's Theory, . 118 
Electro-Magnetic Motions 121 
Henry's Coils, . . 123 
Secondary Currents, . 124 
Electro-Magnetic Tele- 
graph, . . .127 
Magneto-Electricity, . 130 
Thermo-Electricity, . 131 



PART II. 



CHEMICAL PHILOSOPHY. 



Elements and their Laws 
of Combination, 
Combination by Weight, 
Definite and Multiple Pro- 
portions, . 
Equivalent Proportions, 
Table of Chemical Equi- 
valents, . . .13 
Combination by Volume, 
Chemical Nomenclature, 
Names of Compounds, 
Chemical Symbols, 
Chemical Affinity, 
Atomic Theory, . 
Specific Heat of Atoms, 
Crystallization, . 





Crystalline forms, 


155 


133 


Cleavage of Crystals, 


158 


134 


Measurement of Crys- 






tals, 


159 


134 


Isomorphism, 


161 


135 


Chemical Effects of Vol- 






taic Electricity, . 


163 


6-7 


Conditions of Voltaic De- 




138 


composition, . 


164 


140 


Laws of Electrolysis, . 


167 


141 


Voltameters, 


168 


145 


Sustaining Batteries, . 


169 


147 
151 


" « Daniell's, 
Grove's and Smee's Bat- 


170 


152 


teries, 


171 


152 


Electro-Metallurgy, . 


173 



CONTENTS. 

PART m. 

INORGANIC CHEMISTRY. 



Non-Metallic Elements 


$, 175 


Classification, . 


175 


1. Oxygen, . 


176 


Management of Gases 


, 179 


2. Chlorine, . 


181 


Compounds of Chlorine 


with Oxygen, 


185 


3. Bromine, . 


188 


4. Iodine, 


189 


Compounds of Iodine with 


Oxygen, &c. . 


190 


5. Fluorine, . 


191 


6. Sulphur, . 


192 


Compounds with Oxygen, 193 


Sulphurous Acid, 


194 


Sulphuric Acid, 


195 


7. Selenium, . 


199 


8. Tellurium, 


200 


9. Nitrogen, . 


200 


Chemical History of the 


Atmosphere, . 


202 


Compounds of Oxygen 


and Nitrogen, 


203 


Nitrous Oxyd, . 


204 


Nitric Oxyd, . 


205 


Nitric Acid, 


207 


10. Phosphorus, 


209 


Compounds of Phospho- 


rus with Oxygen, 


211 


Other Compounds of Phos- 


phorus, 


212 


11. Carbon, 


213 


Carbonic Acid, 


217 


Carbonic Oxyd, 


220 


Compounds of Carbon 


with the Chlorine Group, 222 


Compounds of Carbon and 


Nitrogen, 


222 


12. Silicon, . 


223 


Sicilic Acid, 


224 


Fluorid of Silicon, 


226 


13. Boron, 


227 


Boracic Acid, . 


228 


14. Hydrogen, 


229 



PAGK 

Nature of Hydrogen, 234 

Compounds of Hydrogen, 235 
Water, . . . 235 
Eudiometry by Hydrogen, 240 
Union of Hydrogen and 
Oxygen by platinum 
sponge, . . . 241 
Oxyhydrogen Blowpipe, 242 
Natural and Chemical His- 
tory of Water, . 244 
Peroxyd of Hydrogen, 246 
Ozone, . . . 247 
Compounds of Hydrogen 

with II. and III. classes, 248 
Action of Hydrogen with 

Chlorine, . . 248 
Hydrochloric Acid, . 249 
Hydrobromic Acid, . 252 
Hydriodic Acid, . 253 

Hydrofluoric Acid, . 254 
Hydrosulphuric Acid, 255 
Ammonia, . . 258 

Phosphureted Hydrogen, 261 
Light Carbureted Hydro- 
gen, ... 263 
Olefiant Gas, . . 264 
Combustion and Structure 

of Flame, . . 266 

Lamps and Blowpipe, 271-2 

Safety Lamp, . . 274 

Metallic Elements, . 275 

General Properties of the 

Metals, ... 276 
Classification of Oxyds, 278 
Theory of Salts, . 279 
Classification of Metals, 281 

15. Potassium, . . 282 
Potash, ... 284 
Salts of Potash, . 287 

16. Sodium and Soda, . 292 
Chlorid, &c. of Sodium, 293 
Manufacture of Glass, 297 

17. Ammonium, . . 298 
Salts of Ammonium, . 299 



CONTENTS. 



PAGE 

Hydrosulphuret of Am- 
monia, . . . 300 

18. Lithium, . . .301 

19. Barium, ... 301 

20. Strontium, . . 303 

21. Calcium and Lime, . 303 

22. Magnesium and Magnesia, 306 

23. Aluminium, . . 308 
Alums, ... 309 
Pottery, . . . 310 

24. Glucinum ; 25. Yttrium ; 

26. Zirconium; 27. 

Thorium; 28. Cerium; 

29. Lantanum, . 311 

30. Manganese, . . 312 

31. Iron, ... 314 

Manufacture of Iron, . 315 

Oxyds of Iron, . . 316 

32. Chromium, . . 318 

33. Nickel, ... 320 

34. Cobalt, ... 321 

35. Zinc, . . , °*22 

36. Cadmium „ . °23 



PAGE 

37. Lead, ... 324 

38. Uranium, . . .326 

39. Copper, ... 326 

40. Vanadium; 41. Tungsten; 
42.. Molybdenum ; 43. Co- 
lumbium; 44. Titanium, 327 



45. Tin, 

46. Bismuth, . 

47. Antimony, 

48. Arsenic, . 
Arsenious 

Arsenic, 



>cid, White 



329 
331 
332 
?34 

334 



Detection o' i* senic as a 
poison, . . . 336 

49. Osmium, ... 338 

50. Mercury, ... 339 

51. Silver, ... 342 

52. Gold, ... 345 

53. Platinum, ... 346 

54. Palladium, . .348 

55. Rhodium, ... 349 

56. Iridium, ... 349 



PART IV. 



ORGANIC CHEMISTRY. 



Introduction, . . 350 

General Properties of Or- 
ganic Bodies, . 350 
Modes of Combination, 352 
Equivalent Substitution, 352 
Monobasic Acids, and 
Substitution by Resi- 
dues, ... 353 
Sesqui-salts, Direct Union, 354 
Isomerism, . . 354 
On the Density of Vapors, 355 
Analysis of Organic Sub- 
stances, . . 357 
Organic Compounds and Pro- 
ducts of their Altera- 
tion, ... 362 



Ammonia, 



362 



Amides, ... 363 
The Group of Alcohols, 

Alcohol, ... 364 
Sulphur Alcohol, . 366 
Action of Acids upon Al- 
cohol, . . .366 
Coupled Acids, . . 367 
Nitric, Perchloric, Hydro- 
chloric Ethers, . 368-69 
Acetene, Nitric Acetene, 

Sulphovinic Acid, 369-70 
Carbovinic Acid, . 370 
Silicic Ethers, Products 
of the decomposition 
of Sulphovinic Acid, 371 
Sulphuric Ether, Letheon, 372 
defiant Gas, . . 373 



CONTENTS. 



X\ 



PAGE 

Dutch Oil, . . 374 

Products of the Oxyda- 

tion of Alcohol, . 375 
Acetic Acid, . . 376 
Acetates, . . 377 

Acetates of Lead, . 378 
Wood-Spirit, or Methylic 

Alcohol, . . 380 

Methylic Ethers, &c, 381 
Oxydation of Wood-Spirit, 382 
Formic Acid, . . 383 
Amylic Alcohol, . 383 

Amylic Ethers, . . 384 
Oxydation of Amylic Acid, 385 
Ethal and Ethalic Acid, 385-6 
On the Relations of the 
preceding Bodies, . 387 
• Bitter Almond Oil, Ben- 

zoilol, . . .388 
Benzamide, Hydrobenza- 

mide, . . .389 
Benzoine, Benzene, Nitro- 
benzene, . . 390 
Oil of Cumin, . . 390 
Oil of Spirea, . . 391 
Salicylol, Salicylic Acid, 391 
Phenol, Oil of Cinnamon, 393 
Sugar, Starch, and Allied 
Substances, . . 394 
Products of the decompo- 
sition of the Sugars, 395 
The Vinous Fermentation, 395 
Lactic Acid, . . 396 
Starch, ... 398 
Dextrine, '. . .399 
Woody Fibre, . . 400 
Xyloidine, Gun Cotton, 

Pyroxyline, . . 401 
Transformation of Woody 
Fibre, Destructive Dis- 
tillation of Wood, . 403 
Kreasote, Paraffine, Coal 

Tar, . . .404 
Petroleum, . . 405 

Fats and the Substances de- 
rived FROM THEM, . 405 

Soaps, Glycerides, Acro- 
leine, . . . 406 

Butyric Acid, Butyric 
Ether, . . .407 

Margarine, Stearine, Ole- 
ine, . . . 409 



Fatty Acids, 
Oleic Acid, 
Soaps, 
Vegetable Acids, . 
Oxalic Acid, 
Oxalate of Lime, 
Tartaric Acid, . 
Racemic, Malic, 
Citric, 

Tannic, Tannin, 
Gallic Acid, 



PAGE 

410 
411 
412 
412 
412 
414 
414 
415 
416 
417 
418 
Volatile or Essential Oils, 418 
Oil of Turpentine, . 419 
Camphene, . . 419 

Juniper, Pepper, Lemon, 

&c. 419 

Camphor, Borneo Cam- 
phor, Oil of Mustard, 420 
Caoutchouc, Gum-Elastic, 420 
Gutta Percha, . . 421 
Coloring Matters, . 421 

Quercitrine, Carthamine, 

Turmeric, . . 422 
Hematoxyline, Carmine, 
Chlorophyle, Lecano- 
rine, Orcine, . . 422 
Indigo, ... 423 
Indigogene, Sulphindigotic 

Acid, Saxon Blue, . 424 
Isatine, Chlorisatine, . 425 
Isatyde, Indine, Anilic 

Acid, . . 425 

Chloranile, . . 426 

Organic Bases, or Alkaloids. 
Constitution and characters 426 
Anilene, Chloranilene, Ni- 

tramline, . . 427 
Quinoline, Nicotine, Co- 
nine, Amarine, . 428 
Cinchonine, . . 428 
Morphine, Codeine, Nar- 

cotine, . . . 429 
Strychnine, Brucine, So- 

lanine, Veratrine, . 430 
Aconitine, Sanguinarine, 
Theine, Caffeine, The- 
obromine, . . 431 
Other Vegetable Principles. 
Amygdaline, Asparagine, 432 
Salicine, Saligenine, Sali- 

retine, . . .433 
Helicine, Phloridzine, 434 



XII 



CONTENTS. 



PAGE 

The Cyan ids, and the Com- 
pounds DERIVED FROM THEM. 
Hydrocyanic Acid, . 435 
Cyanid of Potassium, . 436 
Cyanogen, . . . 437 
Cyanates, Cyanate of Po- 
tash, . . .438 
Urea, ... 439 

Sulphocyanates, Mellon, 440 
Melan, . . .440 
Results of the Complica- 
tion of the Cyanids, 441 
Cyanuric Acid, Melanine,441 
Ammeline, Ammelide, 442 
Complex Cyanids, Ferro- 
cyanids, Yellow Prus- 
siate of Potash, . 442 
Ferro-cyanic Acid, Prus- 
sian Blue, Ferridcyanid 
of Potassium, . 444 

Ferridcyanic Acid, . 445 
Platino-cyanids, . . 445 
Fulminates, Fulminate of 
Mercury, do. Silver, 446 
Alcarsine, and the Bodies 
derived from it. 
Alcarsine, Chlorarsine, 447 
Kakodyle, Alcargene, 448 
Uric Acid, and the Pro- 
ducts .of its Decomposi- 
tion, .... 448 
Allantoine, Alloxan, Al- 

loxantine, . . 449 
Uramile, Murexide, Para- 

banic Acid, . . 450 
Oxaluric Acid, . . 451 
Hippuric Acid, . . 451 
Glycocoll, Gelatine Su- 
gar, Relations of Gly- 
cocoll and Alcargene, 452 
Nutritive Substances Con- 
taining Nitrogen, . 452 



PASS 

Vegetable Albumen, Fi- 

brine, Caseine, &c. 452 
Bread, Yeast, Animal Al- 
bumen, Fibrine,Caseine 453 
Proteine, . . . 454 
Gelatine, Chondrine, . 455 

The Blood. — Red Globules, 
Hematine, Arterial Blood, 456 
Chyle, ... 457 

The Gastric Juice, . 457 
Pepsine, the Saliva, . 458 

The Bile Cholesterine, 458 

Choleic Acid and Cho- 
leate of Soda, . . 458 

The Urine, . . .459 
Calculi, . . .460 

The Brain and Nervous Mat- 
ter, .... 460 
Cerebric and Oleo-phos- 
phoric Acids, . 460 

Milk and Bones, . . 460 
Analysis of Bones, . 461 

Nutrition of Plants and 
Animals, . . . 462 
The Food of Plants, . 462 
Cellular Tissue, . . 463 
Evolution of Oxygen, . 463 
Soils, Inorganic Constitu- 
ents oT Plants, . 463 
Action of Humus, . 464 
Growth of Air Plants, 464 
Fertilizers, Ammonia, Gu- 
ano, . . . 465 
The Digestive Function, 465 
Assimilation of Fats, . 466 
Waste of Tissues, . 466 
Objects of Respiration, 467 
Uses of Oxygen, . 467 
Vital Heat, . . 467 
Balance of Organic Na- 
ture, . . . 468 

Index, . . . .471 



FIKST PKINCIPLES 



OF 



CHEMISTRY. 



PART I.— PHYSICS. 

INTRODUCTION. 

1. Our knowledge of nature begins with experience. 
While this teaches us that like causes, under similar cir- 
cumstances, produce like effects, we also recognise as insepa- 
rable from our experience, the great principle that every event 
must have a cause. Man, " as the priest and interpreter of 
nature,"* seeks to extend his experience by experiment. 
Every experiment is but a question addressed to nature, ask- 
ing for an increase of knowledge ; and if we question her 
aright, we may be sure of a satisfactory answer. 

2. Observation instructs us in a knowledge of the external 
forms of nature, and we thus acquire our first impressions of 
the various departments of Natural History. Our knowledge 
would, however, be very limited, without a constant effort 
to extend our experience by experiment. The ancient 
Greeks and Romans were learned and polished in the intel- 
lectual arts, and excelled in many branches of human know- 
ledge. Their ignorance, however, of the works of nature, 
and the laws by which they are regulated, was extreme ; and 

1. What is the beginning of our knowledge of nature ? What 
great principle do we recognise in connection with experience ? 
What is an experiment ? 2. What does observation teach ? How 
does it extend our knowledge ? What is said of the ancients ? 
Why did they fail ? 



•"Homo naturae minister et interpres." — Bacon. 
2 



14 INTRODUCTION. 

this was because they failed to question her aright : because 
they overlooked the true connection between cause and effect. 
The ancient philosophy abounded in plausible arguments 
regarding those phenomena of nature which could not fail to 
arrest the attention of an intelligent people ; but its reasonings 
were based on an a priori assumption of a cause, and not 
upon an inductive inquiry after facts and their connections. 
It failed to apply itself to the careful collection and study of 
facts in order to science. Facts in nature are the expression 
of the Divine will, in the government of the physical world. 
The universe of matter is made up of facts, which, observed, 
traced out, and arranged, lead us to the knowledge of certain 
laws and forces which proceed directly from the mind of 
God. These are the " laws of nature :" science is but the 
exposition of them, and of science based upon such grounds, 
the ancient Philosophy was completely ignorant. 

3. It is important to distinguish that knowledge which is 
purely intellectual in its character, from that which results 
from observation and experience. Speaking of this subject, 
one of the most learned of living philosophers says : " A 
clever man, shut up alone, and allowed unlimited time, might 
reason out for himself all the truths of mathematics, by pro- 
ceeding from those simple notions of space and number, of 
which he cannot divest himself, without ceasing to think ; but 
he could never tell, by any effort of reasoning, what would 
become of a lump of sugar, if immersed in water, or what 
impression would be produced on the eye, by mixing the 
colors yellow and blue." — (Herschel.) We may, however, 
with propriety doubt, whether there is any knowledge or 
philosophy so purely intellectual, or absolute, that it does not 
imply some previous recognition of physical facts. 

4. The physical philosopher is also of necessity an intel- 
lectual philosopher. The observation of facts forms only the 
foundation of science, and a fact isolated and unexplained has 
no scientific value. The knowledge of physical laws deduced 



Characterize the ancient philosophy. On what was its reasoning 
based ? How did it fail ? What are facts ? How do we detect the 
laws and forces of nature ? From whence do these proceed ? 
What is science ? 3. What convenient distinction is named ? 
What remark is quoted in illustration of this ? What doubt may 
we entertain ? 4. What is said of the physical philosopher ? 
What of observation ? What of an isolated fact ? 



INTRODUCTION. 15 

from the study of observed facts will enable the philosopher 
to foretell the result of the possible combination of those 
laws, and to assign reasons for apparent departures from 
them. In this way discoveries are predicted and detailed ; 
observation is anticipated, and called on to verify the alleged 
discovery. The perturbations of the planet Uranus indicated 
the existence of some body in space heretofore unknown. 
When Le Verrier had reconciled these disturbances with the 
supposed influence of a new planet, and determined its ele- 
ments of motion, he had as truly discovered the remote sphere 
which now bears his name, as when the German astronomer, 
by pointing his telescope to the precise place in the heavens 
which Le Verrier had designated, announced to the world 
that the stupendous prediction was verified by observation. 
In like manner, a familiarity with chemical laws enables the 
chemist to foretell the result of combinations which he has 
never investigated, and in some cases even to assign the con- 
stitution of bodies which he has never analyzed. 

5. Our knowledge of nature is conveniently classified 
under three great divisions, which are, Natural History, 
Mechanical Philosophy, and Chemistry. The first teaches 
us the characters and arrangement of the various forms of 
animal and vegetable life and minerals, giving origin to the 
sciences of Zoology, Botany, and Mineralogy. Mechanical 
Philosophy explains the laws which govern masses of 
matter, without considering of what that matter is composed. 
It tells us how bodies fall to the earth, — how liquids spout 
from an orifice ; it explains the power of the lever, the screw, 
and the inclined plane ; it teaches us the mechanical laws 
of the atmosphere and of the celestial bodies, the phenomena 
of tides and currents and the winds ; but it tells us 
nothing of the nature of the various substances of which it 
treats. 

Chemistry begins where the natural sciences end. It teaches 
us the intimate and invisible constitution of bodies, and 
reveals to us the compounds which may be formed by the 



What does a knowledge of natural laws enable the philosopher to do ? 
What happens in this way ? Illustrate this in case of the perturba- 
tions of Uranus. When had Le Verrier truly made his discovery ? 
What can the chemist do ? 5. How is our knowledge of nature 
classified? What does the first teach? Mechanical philosophy 
teaches what ? Define the province of Chemistry. 



16 matte re- 

union of simple substances, and the laws of their combination. 
It investigates the forces resident in matter, and which are 
inseparable from our idea of molecular action, — forces whose 
play produces the phenomena of Light, of Heat, and of 
Electricity. Chemistry also unfolds the wonderful operations 
of animal and vegetable life, so far as their functions depend 
upon chemical laws, as in the processes of respiration and 
digestion. 

While we now direct our attention to Chemistry, we 
naturally inquire, What is Matter ? 

I. MATTER. 
1. General Properties of Matter. 

0. Experience, founded on the evidence of our senses, has 
convinced us of the existence of matter. We feel the 
resistance which it offers to our touch ; we see that it has 
form, and occupies space, and hence we say it has extent ; 
and, lastly, we attempt to raise it, and we find ourselves 
opposed by a certain force which we call weight. 

Matter possesses extension, because it occupies some space. 
It is impenetrable, because one particle of matter cannot 
occupy the same space with another at the same time. It 
has gravity, because it obeys the law of universal gravitation. 
Whatever, therefore, possesses these three qualities, is matter. 

7. Let us look at these qualities a little more attentively. 
The largest and most solid masses of matter, even entire 
mountains, may be ground down by mechanical force to dust 
so fine that the winds will bear it away ; but each minute 
particle still occupies some space, and we may imagine that 
a great multitude of smaller particles may still be formed 
from its further division. A grain of gold may be spread 
out so thin as to cover 600 square inches of surface on silver 
wire, and an ounce can in this manner be made to cover 
1300 miles of such wire. One grain of green vitriol, 

What is its relation to the powers of matter ? It also unfolds what 
of life ? What inquiry naturally arises in commencing the study of 
Chemistry ? 6. What evidence have we of the existence of matter ? 
What three qualities are named as belonging to matter ? What is 
extension ? What is impenetrability ? What do we mean by weight? 
7. If we reduce solid matter to dust, do we destroy its quality of 
extension ? Give an illustration in the case of gold, of the divisibi- 
lity of matter. 



GENERAL PROPERTIES OF MATTER. 17 

(sulphate of iron) dissolved, and diffused in 20 million grains 
of water, will still be easily detected by the proper tests. 
The delicate perfume of musk, which is due to matter in an 
exceedingly fine state of division, has been known to remain 
for many years in a drawer or apartment, and still to emit 
very decided fragrance. Of course it had continued to give I 
its appropriate odor during the whole time; and, being 
invisible at first, we may form some idea of the wonderful 
minuteness of each particle. 

The organic world also presents us with beautiful exam • 
pies of the great divisibility of matter, in the remarkable forms , 
of animalcules revealed by the microscope, many millions of A 
which can be embraced in a single drop of water. Yet eaefa^ » 
of these inconceivably minute organisms has its own .muscu- 
lar, digestive, and circulatory systems. How minute, then, 
the ultimate particles, of which many myriads must be con- 
tained in each animalcule ! 

It is, however, maintained, that matter is not infinitely 
divisible ; for none of the attributes of infinity can be predi- 
cated of that which is finite. 

8. Molecules, or Atoms. — Every mass of matter," how- 
ever minute, is composed of a vast number of extremely 
minute particles, which we call molecules,* or atoms. What- 
ever size these particles may possess, they are the centres of 
all the forces or powers whose united effect gives matter 
all its known properties. We can, however, form some idea 
of the relative size and weight of these molecules, as is made 
evident by the laws of chemical combination ; and the laws 
of crystallization also reveal the fact that they have an 
inherent difference of form, some being spherical while 
others are ellipsoidal. 



Give another illustration in the case of iron. A third case (the 
perfume) is mentioned. What illustration does the organic world offer i 
Is matter then infinitely divisible ? 8. How is every mass com- 
posed ? What is a molecule ? What is said of them ? What do 
we know of their relations ? What further do the laws of crystal- 
lization show ? 

* Molecule, a diminutive, from moles, a mass. This term is pre- 
ferable to ' atom' or ' ultimate particle 5 as implying no theory, which 
both the others do. Atom is from a privative and temno, I cut, sig 
nifying their supposed indivisibility. 

2 * #&*&&* 



18 MATTER. 

We know that matter of all sorts is influenced by the laws 
of universal gravitation. It is the constant operation of this 
law on matter which gives it the property that we call 
weight, which is the measure of the force required to over- 
come the attraction of gravitation. This force, in the 
language of natural philosophy, is said to be directly as the 
quantity of matter,- and inversely as the square of the 
distance. The weight of a body is therefore dependent on 
the number of molecules or atoms which it contains. 

9. Indestructibility of Matter. — No particle or atom of 
matter can ever be annihilated or destroyed. The same omni- 
potence which called it into being is required to destroy it. 
But, it may be asked, do we not see matter daily perishing 
before us in our fires, and vanishing in smoke and vapor? 
Its forms do indeed vanish from our sight, but it is not lost ; 
and we shall learn, when we come to attend to the beautiful 
phenomena of life, by how divine an arrangement the winds 
and the rains gather up their lost atoms, and restore them to 
the earth, thus clothing it with new beauty. 

10. Cohesion. — The power of gravitation just mentioned, 
acts alike on all matter, and at all distances. But the power 
which holds together the several particles of matter which 
form a solid mass, acts on particles of a like kind, and at 
insensible distances. This attraction of aggregation is called 
the force of cohesion, — that power which we must overcome 
before we can reduce a piece of marble or lead to dust or 
smaller fragments. Opposed to this force, which would 
draw together and keep united all the particles of a body, we 
have the power of repulsion, whose tendency is to separate 
these particles from one another. 

In illustration of the first of these powers, if we press together 
two smooth surfaces of lead, clean and bright, as for example 
the halves of a bullet cut through, they will adhere or unite 
together so firmly as to require the power of several pounds 
weight to draw them apart. The plates of polished glass, 

"What law influences all matter ? What property in bodies is due 
to this law ? On what does the weight of a body depend ? 9. What 
of the destructibility of matter ? What becomes of the matter 
burnt or turned into vapor ? Is it lost ? How shall we prove this ? 
10. What other power of attraction is here mentioned ? How dif- 
fering from gravitation ? Among what particles exerted ? What is 
it called ? What opposing force have we ? Its tendency is what ? 
What example illustrates the attraction of aggregation ? 



GENERAL PROPERTIES OF MATTER. 19 

also, which are prepared for large mirrors, if allowed to 
rest together, with their surfaces in close contact, havf 
been known to unite so firmly as to break before they woulJ 
yield to any effort to separate them. This is owing to 
the force of attraction between the particles of the same 
kind, called homogeneous attraction, or the attraction of ag- 
gregation. 

11. Repulsion. — We see the second of these opposing 
powers, namely, repulsion, in one of the common effects of 
Heat. This power is able to overcome the strongest attrac- 
tion, and to separate, to a great distance, the particles before 
closely united. Heat will convert ice into water, and the 
water into invisible vapor. The most solid metals cannot 
resist its power ; and yet, when it ceases to operate, the an- 
tagonist power of attraction again draws the separated parti- 
cles together, and restores the original form. 

12. Chemical Attraction. — Matter is, however, governed 
by another and yet more powerful force of attraction, namely, 
the power of affinity, or chemical attraction. It is unlike 
the power of gravity, because it acts only at invisible dis- 
tances, and is also unlike the power of cohesion, (attraction 
of aggregation,) because it exists only between particles of 
different kinds. Gravity acts on all matter and at all dis- 
tances. Cohesion acts only on the same kind of matter at 
insensible distances. Chemical affinity acts only between 
unlike particles at insensible distances. 

13. The action of this marvellous power of chemical affi- 
nity, results in producing from two unlike particles or atoms 
of matter, a third body having no resemblance in any of its 
properties to either of the other two constituent particles. The 
compound molecule of the new body acts the part of a simple 
molecule, in its relation to other bodies. To follow out all 
the wonderful results of this power of affinity, and make 
ourselves acquainted with all the new bodies which are 
formed under its influence, constitutes the proper business of 



Another also ? "What othei name is there for this sort of attrac- 
tion ? 11. What does heat show us ? How does it act ? What 
changes will it produce on .vater ? If removed again, what happens ? 
12. What other force, still, governs matter ? Differs from gravity 
and aggregation in what ? Contrast these three sorts of attraction 
by their actions. 13. What is the result of chemical affinity ? What 
properties has the third body? 



20 MATTER. 

the chemist. To do this, we must first become familiar with 
a number of other important subjects. 

14. Elements. — If we could imagine a world to exist, com- 
posed wholly of lead or of iron, and capable of supporting human 
life, it would afford no opportunity for the study of the science 
of chemistry, which owes its existence to the fact that matter 
is various and not simple. We learn not only that there are 
different kinds of matter in the world, but also that nearly all 
the forms in which we see it in nature, or in which we make 
it combine by art, are capable of being reduced to a few sim- 
ple substances, which are called elements. An element is a 
form of matter which has hitherto resisted all attempts to ob- 
tain from it any thing more simple. The number of such 
bodies at present known is fifty-six, and of these all things -are 
made. The progress of science may show us, by improved 
methods of investigation, that some of our elements are com- 
pounds, or, on the other hand, some new ones may be dis- 
covered. Water was one of the four elements of the ancients, 
(earth, air, fire, and water.) We now know that water is a 
compound of two gaseous elements, (oxygen and hydrogen.) 
Gold is an example of what we suppose to be an element. 
We can alter its form by combining it with other substances, 
thus making it part of a new compound, but no process has 
ever enabled us to show that it is itself a compound. The 
process by which a body is shown to be compound, is 
called analysis ; and that by which the same body is repro- 
duced, by the direct union of its elements, is called synthesis. 
Where these two modes of proof are united, the evidence 
obtained is of the very highest kind. 

15. Imponderable Agents.— Besides the elementary mat- 
ter of the world of which we have already spoken, there 
are certain other agents of so subtle a nature that they 
possess none of the common properties of matter. These 
are Light, Heat, and Electricity ; they are frequently called 



14. What if the world were made of iron or lead ? To what does 
chemistry owe its existence ? What do we learn of matter ? Are 
things about us generally simple or compound ? In what sense is 
the term element used in chemistry ? Do we positively know any 
element ? What illustration is named of the elements of the an- 
cients ? What is gold ? How can we alter its properties ? What 
is analysis ? What synthesis ? What is the best kind of proof in 
chemistry ? 15. What other agents are there besides those already 
mentioned ? What have they been called ? 



THE THREE STATES OF MATTER. 21 

imponderable agents, because we have never been able to 
collect and weigh them. Of their real nature, it must be 
remembered, we know nothing. We shall treat of them as if 
they were matter, because the language of science accords 
with this mode of presenting their phenomena. Late investi- 
gations countenance the opinion that they are inseparably 
connected with the existence of matter, and should be classed 
philosophically with its general powers or forces. Chemical 
affinity has been considered identical with electricity. It is 
also considered as an established fact in science, that there 
exists, throughout all space, an extremely rare elastic medium, 
called ether, whose vibrations cause the phenomena of light. 
Whatever may be the ultimate fate of this opinion, it is found 
to accord with the most mathematical exactness with all the 
phenomena of optics. 

2. The Three States of Matter — the Solid, Fluid, and 
Gaseous. 

' 16. The three common conditions, or states, in which 
matter is known to us, are the solid, fluid, and gaseous. In- 
deed we may reduce them simply to solids and fluids, if we 
choose to consider fluids as of two sorts, elastic fluids, as air 
and vapor, and inelastic fluids, as water and other liquids. 
We have already hinted that these several states of matter 
depend on the power of heat. (11.) This cause will be more 
fully considered in the chapter on heat. 

17. Properties of Solids. — It is the distinguishing property 
of solids to have their particles bound together by so strong 
an attraction as in a great measure to destroy their power of 
moving among each other. 

No solid, however, not even gold and platinum, which are 
the most compact solids known, has its particles of matter 
so aggregated as to be incapable of some condensation. 
Blows, pressure, or a reduction of temperature, will condense 
almost all solids into a smaller bulk, and water may even be 



What of the nature of these ? What have we reason to believe ? 
What is said of a pervading ether ? v /}6. Name the three states of 
matter. Reduce them to two. Distinguish between the two classes 
of fluids, and give an example. What cause is suggested for these 
different states of bodies ? 17. What is said to be the distinguish- 
ing feature of solids ? What is said of the most compact bodies ? 
How can they be diminished in bulk ? 



22 MATTER. 

forced through the pores of gold, by very great mechanical 
pressure. All solid bodies are, therefore, considered as 
porous, and their particles are believed to touch each other in 
comparatively few points. 

18. Solids possess several other properties which may be 
considered in. one way or another as modifications of the 
power of cohesion. (10.) (1.) Hardness; this property is 
possessed by solids in very various degrees, from the diamond, 
the hardest of all substances, to those solids which are so soft 
as to be easily scratched by the finger-nail, as lead and some 
minerals. Hardness has no connection with weight or densi- 
ty, for lead is more than three times as heavy as the diamond. 
(2.) Elasticity ; or the power of assuming their original form 
after being bent or compressed. It is found in all degrees of 
perfection, from glass and steel, which are almost perfectly 
elastic, to lead, which possesses none of this quality. (3.) 
Brittleness is often closely connected with the last property. 
If glass or steel be bent beyond a certain degree, it breaks 
suddenly : this point is the limit of their elasticity. (4.) Mal- 
leability, or the capability of being beaten by blows into thin 
leaves, is found in the highest perfection in gold, and in a 
good degree in many other metals ; 300,000 leaves of gold 
are but an inch thick ; while an equal number of leaves of 
common letter paper would be several rods in thickness. (5.) 
Ductility and laminability are properties closely allied to 
malleability. Iron, for instance, unless heated, cannot be 
beaten like gold, but it may be drawn into fine iron wire (duc- 
tility) and plated by rollers into thin sheets, (laminability.) 

19. Fluids. — Fluids are distinguished from solids by the 
perfect freedom of motion among their particles. We have 
said (16) that fluids may be divided into two classes ; liquids, 
like water, and gases or vapors, like air and steam. The 
first is inelastic, or very nearly so ; the second highly elastic. 
We will consider them separately. 

20. Liquids press with equal force on all parts of a vessel 



What proof of the porousness of gold ? What of solids in general ? 
18. Of what force are the several properties connected in this sec- 
tion modifications ? Enumerate these properties. What is hard- 
ness ? Give an example. Is it connected with weight or density ? 
(2) What is elasticity ? (3) Brittleness ? (4) Malleability ? Give 
an example and a comparison. (5) How do ductility and laminabi- 
lity differ from malleability? 19. Distinguish fluids from solids. 
Classify them. (16.) 20. How do liquids press on a containing vessel? 



THE THREE STATES OF MATTER. 23 

containing them. If an attempt be made to condense water, 
for instance, in a tight vessel, the pressure exerted for this 
purpose will at once be felt in every part of the fluid, and on 
all sides of the containing vessel to the same degree as on the 
portion where the power is applied. Liquids are said to be 
inelastic ; but this is not strictly true, for water may be com- 
pressed, in the refined apparatus of QErsted, one part in 
22,000 for every atmosphere of pressure, and the water in a 
vessel sunk to the depth of 1000 fathoms (6000 feet) in the 
sea, has been compressed to nineteen-twentieths of its origi- 
nal bulk. For all practical purposes, however, water and 
other fluids are inelastic, so that they may be applied to exert 
immense power in the hydrostatic press. 

21. Capillary attraction is a property possessed by fluids 
as distinguished from, solids. By this property, fluids will 
mount in small tubes (called capillary or hair tubes, from 
the hairlike fineness of the bore) to a considerable height 
against the power of gravity. It is this power which enables 
wood and other porous bodies to draw up into their pores any 
fluid with which they may come in contact. Water standing 
in a tumbler has its surface made concave, being raised by 
capillary attraction at the edges where it comes into contact 
with the glass. 

The capillary force is so great, that plugs of dry wood 
driven into holes bored for the purpose, in rocks, and then 
saturated with water, swell so much from the quantity of 
water drawn into the pores of the wood, (by capillary attrac- 
tion) as to burst open the rocks. By the same power, a lamp 
or candle draws up its supply of fuel. A solid bar of lead, 
bent like the letter U, and one end of it put into a vessel of 
quicksilver, (the only metal which is a fluid at common 
temperatures,) after some time becomes so saturated with 
the mercury by capillary action, as to convey it out of the 
vessel, like a syphon. 

When surfaces are wet by water or oil, or any other fluid, 
it is by virtue of this power ; and we see from this that the 
capillary power is closely connected with chemical affinity, 

Give an illustration. What is said of the elasticity of liquids ? 
What of that of water ? How may they be considered, however ? 
21. What is capillarity ? Define the word. How is the power 
seen in a tumbler of water ? Also in lamps and candles ? Give an 
illustration of this power in wood. What experiment is mentioned 
with lead ? What is said of the wetting of surfaces ? 



24 MATTER. 

(or heterogeneous attraction.) Mercury, for instance, will 
not wet or cover the surface of glass or the skin, nor of iron ; 
but it at once wets lead, tin, gold, silver, and many other 
metals. Glass can be wet by water only with some difficulty : 
oil, however, easily wets glass, and after this, water cannot 
be made to adhere to its surface at all. 

22. The cohesion of the particles of a liquid for each 
other, is well shown by the globular form of the dew-drop : 
the power of cohesion, (or homogeneous attraction) tending 
to bring all the particles to a centre, produces a sphere. A 
soap-bubble is a beautiful example of the cohesive power of a 
thin film of liquid. Soap-water is more viscid, but not more 
coherent than pure water, and the bubble may be considered 
as a large drop of water, with all its interior removed, and 
the place supplied with air. The cohesive power of the 
particles of water in the film of the bubble is so great, that 
if the pipe be taken from the mouth before the bubble leaves 
it, a stream of air will be driven forcibly from the bore of the 
pipe, by the contraction of the film. 

23. Elastic fluids are either gases or vapors. A gas is 
matter in a permanently aerial form. A vapor is matter 
temporarily in an aerial form. The same physical laws 
govern both, and we will briefly review them. 

24. The Atmosphere and Laws of Gases. — We live on 
this planet at the bottom of a vast ocean of gaseous matter, 
which we call the air, or our atmosphere. It surrounds us 
everywhere, and presses upon us with a weight which, when 
stated in numbers, seems beyond belief. Under its influence, 
all operations, chemical as well as mechanical, are performed. 
It penetrates deeply into the crust of the earth itself, and is 
largely dissolved in all its waters. Its chemical composition 
will be discussed in its proper place, when we come to con- 
sider the properties of the two elements of which it is princi- 
pally composed. 



How is it connected with capillarity ? Give an illustration in 
mercury, and in oil and water on glass. 9.2. How is the power of 
cohesion shown in liquids ? What is said of the soap-bubble ? 
How may we consider the bubble ? What is said of the cohesive 
power of the film ? How is this well illustrated ? 23. What are 
elastic fluids ? (16 and 19.) Define a gas. Define a vapor. 24. To 
what is the air compared ? What is said of it ? Is it confined to the 
surface ? 



THE ATMOSPHERE. 



25 



25. It is usual to speak of a vessel or apartment which 
contains air only, as empty. It is easy to show, however, 
that the so-called empty space is in reality full, and that the 
matter it contains is just as capable of being weighed, trans- 
ferred, and rendered sensible by its resistance to other bodies, 
as any other form of matter. If we plunge a bell-glass or 
inverted tumbler into water, holding its mouth horizontally 
downwards, we shall find a resistance to its descent, which 
arises from the air confined within it. The water will rise in 
the vessel to a certain height, which varies with the degree 
of pressure we apply. The deeper we sink the glass, the 
higher will the water rise in its interior, and the less space 
will the air occupy : as we diminish the pressure, the air, by 
its elasticity, returns to its former dimensions, and entirely 
displaces the water. 

26. Elasticity of the Air. — Suppose the two tight-bot- 
tomed hollow cylinders a and &, in the annexed figure, to be 
filled with air : if we fit a plug so 
tightly to the sides of both, that no 
air can pass between it and the sides 
of the cylinder, and then try to force 
down this plug by pressure on the ~ 
stem, we shall find a resistance to 
itg downward motion. The plug, ! 
or piston as it is called, descends 
indeed, but with increasing resistance 
as it goes down ; and if the pressure 
be removed, it returns to its former 
position, suddenly and with force. 
We have thus demonstrated not only 
that the air is a material substance, 
offering resistance, but also, that it is a b 

an elastic substance, capable of compression to an indefinite 
extent, and of restoration to its former condition on the with- 
drawal of the pressure. 

27. The elasticity of the air may also be shown by placing 
the piston in b, in the position represented in the drawing, the 
air beneath it being in the same state of pressure as that 





What is said of a so-called empty vessel ? How can we illus- 
trate the presence of air in an empty vessel l 26. Explain the 
mode by which the elasticity of the air is shown in this section. 
27. How is its elasticity shown in the cylinder b (26) ? 
o 



26 



MATTER. 



above ; if we now attempt to raise the piston, the air which 
before filled only one-half of the cylinder, will expand and 
fill the whole ; and this would be the case, if at the com- 
mencement of the experiment only one-thousandth part of the 
vessel contained air. The tension of the expanded portion, 
as it is termed, would then be only one-thousandth part of 
ordinary air at the earth's surface. We thus learn that air, 
and also many other gases, are perfectly elastic ; although, 
as we shall see further on, there are a number of gases 
which can, by great cold and pressure, be reduced to liquids, 
and some of them even to a solid form. 

28. Air-Pump. — The remarks just made serve also to ex- 
plain the principle and construction of the common air-pump, 
an instrument of great importance to science. In order to 
make an air-pump of one of the cylinders already described, 

it is necessary only to open 
a communication in the 
bottom of the cylinder, 
with some vessel from 
which we wish to remove 
the air, and also to open a 
hole in the piston commu- 
nicating with the external 
air. Each of the holes* is 
covered with a little flap 
or lid of leather or oiled 
silk, fitting the orifice close- 
ly, and called a valve. 
Both these valves open 
freely in an upward direc- 
tion, but the lower one is 
tightly closed by the least downward pressure. In the an- 
nexed figure this arrangement is shown. We have a glass 
vessel, (called an air-receiver,) from which we wish to re- 
move the air. The receiver is made to fit tightly by its edges 
on the metallic plate, from which passes a tube forming a 
connection with the bottom of the cylinder, where, as shown 
in the above figure, the lower valve is placed. Suppose the 




How does half the air fill all the space ? To what extent will this 
occur ? What term expresses the degree of elasticity ? 28. What 
important instrument ' do the foregoing principles explain ? How 
may one of the cylinders a or b (26) be made into an air-pump ? 
Explain the construction and use of the same in the figure. 



THE ATMOSPHERE. 27 

piston to be in the place shown in the figure, and that we 
attempt to raise it by the rod : as it rises, the air beneath it 
expands, to fill the enlarged space, and with it the air in the 
glass vessel and tube also expands, while the little valve at the 
bottom allows the air to pass freely into the cylinder from 
the glass, to supply the vacancy occasioned by the rise of 
the piston. If we now press the piston down, the air beneath 
in the cylinder cannot return into the receiver by the lower 
valve which opens only upward, and, with the least downward 
pressure, closes the opening tight ; but the valve in the piston 
itself now opens outwardly, the air beneath passes out and 
escapes, while the piston descends freely to the bottom of 
the cylinder. We may now raise it again, when a fresh por- 
tion of air will come in from the glass vessel, and be again 
expelled through the piston-valve, when the piston is again 
pushed downwards. By continuing this process, we pump 
out the greater part of the air, as with a common pump we 
draw water from a well. We cannot, however, remove all 
the air in this way, because, as just explained, the smallest 
quantity of air will expand so as to fill the entire space. 
This process is called exhaustion. 

29. Vacuum. — The space thus produced by exhausting 
the air is called a vacuum, or empty space ; a perfect va- 
cuum, however, cannot be formed in this way, although the 
air-pump can produce an exhaustion which answers all the 
purposes of science and art. Many forms of the air-pump 
are in use, all, however, depending upon the principles ex- 
plained. One of the most common is that in which two 
pistons are so arranged (see fig. in 26) as to work up and 
down alternately, being moved by a winch and toothed wheel. 
Sometimes the cylinders are formed of heavy glass tubes, 
which enable the student to see the manner in which the pis- 
ton and valves move, and better to understand the operation. 
The air-pump depends entirely on the elasticity of the air for 
its successful operation. 

v 30. Law of Mariotte. — -The volume or bulk of air at a 
given temperature, depends on the pressure to which it is 
subject, or, in other words, the volume of the air is always 



What raises the valves ? On pressing the piston down, why does 
not the air return ? How does the air beneath it escape ? What is 
the process compared to ? What is it called ? 29. What is the 
empty space called f Why cannot a perfect vacuum be formed ? 



28 



MATTER. 



inversely as the pressure, while the density is directly as 
the pressure. This is called the law of Mariotte, who was 
the first accurately to demonstrate it by ex- 
periments. The annexed figure shows the 
simple apparatus used by him for this pur- 
pose. It is a glass tube turned up and sealed 
at the lower end : a graduated scale of equal 
parts is attached to it. Mercury is poured 
into the open end of this tube so as to rise 
just to the first horizontal line, and a portion 
of air of the ordinary elasticity is thus en- 
closed in the short limb of 9 inches. Now 
if mercury be poured into the longer leg, so 
that it may stand at 30 inches (33) above 
the level of the mercury in the shorter leg, 
it will press with its whole weight on the 
included air, which will then be found to 
occupy 4^ inches, only half of its former 
space. If, in like manner, the column of 
mercury be increased to twice this length, 
its pressure on the included air will be tri- 
pled, and the space occupied by it will be 
reduced to one-third, and so on in simple 
proportion. 

31. Weight of the Atmosphere. — It has 
been abundantly shown by the experiments 
already explained that the air has weight. 
The first movement of the air-pump will fix the 
air-glass on the plate of the pump, and after 
a tolerable exhaustion is produced, great 
force will be required to remove the jar, and 
the pump itself may often be lifted by it. 
The power that holds the air-jar down is 
only the weight of the air pressing upon the 
_jgi — 7 upper side of the glass, while that pressure 
-Jj? Jf is removed from the inside of the glass, by 
j flr the action of the pump ; an upward pressure 
-""WWW is also exerted upon the under side of the 
board or plate of the pump, thus co-operating with the down- 



I 



30. What is meant by the volume of air ? On what does it de- 
pend ? State the law in precise terms. What is this law called ? 
Explain the apparatus which illustrates it. 31. How do we know 
that air has weight ? 




THE ATMOSPHERE. 29 

ward pressure upon the glass receiver. The leather by which 
boys raise large stones and bricks, acts in the same way. The 
leather adheres to the stone only because the air is pressed 
out from the surfaces of contact, and rests with. all its weight 
on the upper side. The difficulty which we experience in 
raising our feet from a wet clay soil, is due in a degree to 
the same cause ; and if the air could be perfectly removed 
from beneath our feet, we should be as firmly and immoveably 
planted on the earth as a well-rooted tree. 

The weight of the air is also well shown by the burst- 
ing of a piece of bladder-skin tied tightly over the mouth 
of an open jar on the plate of the air-pump. 
As the pump is worked, the flat surface of the 
bladder becomes more and more concave, and at 
length bursts inward with a smart explosion. The 
same accident would befall the glass jars used on 
the air-pump, if they were not made of strong 
glass, and arched in form. Thin square glass bottles are 
blown purposely to show this, and burst under the air-pump, 
being either crushed inward by removing the air, or bursting 
outward by the expansion of the contained air, when they are 
surrounded by a vacuum. 

32. We can also determine the weight of the air by ex- 
hausting a small glass globe fitted by a stop-cock to the pump. 
Suppose such a globe to hold 100 cubic inches of air at the 
medium temperature and pressure : if we weigh it before and 
after exhaustion, we shall find, if the vacuum be perfect, that 
it has lost nearly 31 grains of weight, which it regains on 
allowing the air to enter; hence we learn that 100 cubic 
inches of air weigh about 31 grains. By using other gases 
besides air, we ascertain by a similar experiment their rela- 
tive weights and specific gravities, (49, and figure in the 
same section.) 

33. Barometer. — The Barometer* is an instrument by 
which, on principles just explained, we actually measure the 

What force holds down the receiver of the pump ? Explain the 
action of the leather " sticker." Why is it difficult to raise our feet 
in wet clay ? Give another experimental illustration of the weight 
of the air. 32. How may we illustrate its weight accurately ? 
How much do 100 cubic inches weigh ? 33. What is the barome- 
ter ? Give its definition. 

* From the Greek, baros, weight, and metron. measure. 
3* 



30 MATTER. 

weight of the atmosphere. This instrument was invented 
A. D. 1643, by a celebrated Italian philosopher, named Torn- 
celli. Philosophers up to this time, when called to explain tha 
phenomena of the atmosphere and the rise of water in 
a common pump, had contented themselves with say- 
ing that " Nature abhors a vacuum ;" but a well- 
digger in Florence informed Torricelli, that he coula 
raise water in a pump only 33 feet, and this philoso- 
pher at once reasoned, that if nature abhorred a va- 
cuum, there was no reason why she should cease to 
abhor it when it was more than 33 feet high. He in- 
ferred that this column of water must be equal in weight 
to the entire height of an atmospheric column of equal 
size. To prove this experimentally, it was only 
necessary to use a fluid so much heavier than water, 
as to bring the height of the column down to con- 
venient dimensions. Mercury, which is 1 3|- times 
heavier than water, was the fluid selected. A strong 
glass tube about 3 feet long, sealed at one end, was 
filled with mercury. The finger being placed on 
the open end as a stopper, the tube was inverted, 
and the mouth immersed in a small vessel of mer- 
cury. On withdrawing the finger, the mercury in 
the tube sank a certain distance, oscillated up and 
down, and finally came to rest at the height of about 
30 inches from the surface of the mercury in the 
outer vessel. The empty space above the mercury is 
the most perfect vacuum that can be produced, and is 
called the Torricellian vacuum, in honor of the 
discoverer of the barometer. If water were em- 
ployed instead of mercury, it would require a tube 
about 33 feet long. 
34. Determination of the Pressure of the Atmosphere. — 
Water and mercury are supported at these respective 



"Who discovered it, and when ? What explanation has been be- 
fore given of atmospheric pressure ? What observation did the 
well-digger of Florence make ? How did Torricelli explain it? 
What simple experiment did he choose, to prove his inference ? Ex- 
plain the arrangement of apparatus in the figure. What happened in 
withdrawing the finger ? At about what height will the vibrating 
column of mercury stand ? What is the space above the mercury 
called ? If water were used, how long a tube would be required ? 34. 
What sustains the mercury or water, the tube being open at bottom ? 



THE THREE STATES OF MATTER. 3i 

heights by the weight or pressure of the air on tire surface of 
the fluid. Such a column of mercury becomes thus an exact 
counterpoise for the weight of the atmosphere. If the tube 
had the area of one inch exactly, and the mercury in the 
barometer tube stood at 30 inches, we should find that 
fifteen pounds of mercury would be required to fill the tube. 
The pressure of the air, then, on the surface of the mercury, 
is capable of supporting a column of that metal weighing fifteen 
pounds. This is also the weight of a column of air of the 
same size, reaching to the supposed limits of the atmosphere. 
Every square inch of the surface of land or sea is therefore 
subject to a pressure equal to fifteen pounds, or to a column of 
mercury 30 inches in height. A man of ordinary size has a 
surface of about 15 square feet, and he must consequently 
sustain a pressure on his body of about 15 tons. This pro- 
digious load he bears about with him unconsciously, because 
the mobility of the particles of air causes it to bear with equal 
force on every part of his body, beneath his feet as well as 
on his head, and in the inner cavities as well as on the 
outer surface ; if it were not so, great inconvenience and even 
death must result. We can easily feel the pressure of the 
atmosphere on our own persons, by placing one of our hands 
over the mouth of an air-jar, as is seen in the annexed figure, 
when a single stroke of the pump will 
firmly fix the hand, which seems drawn in 
by #hat we are accustomed to call suction, 
but which we now see to be only the 
external pressure of the atmosphere. On 
letting the air in again, we cease to feel 
this sensation, because the balance or equi- 
librium of pressure is restored. 

35. The pressure of the air at the surface is not a constant 
quantity. This is shown by the barometer, the mercury in 
which will be found to vary in height at different times as 
much as 2 or 21 inches between one extreme and another. 
This variation arises from the fact, that the quantity of air 

How much mercury is a counterpoise to the atmosphere, and in how 
long a tube, of what diameter ? Whence we infer what about the 
pressure on the surface of every thing ? A man sustains what load 
of air '! Why are we unconscious of this, and why does it not crush 
us ? We can convince ourselves of the reality of this by what sim- 
ple experiment ? What is meant by what we commonly call 
suction ? 




32 MATTER. 

varies from time to time at the same places, owing to meteo- 
rological causes which this is not the place to discuss ; but 
hence arises the value of the barometer as a weather-glass, 
and to show with precision the amount of atmospheric pressure 
at any given time. The barometer is also of great use in 
measuring the heights of mountains ; because it will be seen 
from what has been already said, that the air at the level of 
the sea must weigh more than on a high hill, since the 
former is pressed down by and supports the weight of the 
entire atmosphere, while on the mountain top we have risen 
above a certain portion of the entire weight of the air. The 
air grows more and more rare as we ascend, and the ba- 
rometer falls in exact proportion. The inconvenience which 
travellers have experienced in ascending high mountains has, 
it is said on good authority, been very much exaggerated. 
The heart continues its action under a diminished external 
pressure, and no serious consequences, it 'is believed, ever 
follow, as the bursting of blood-vessels or lesion of the lungs, 
as some have asserted. On the summit of Chimborazo, 
Baron von Humboldt found that his barometer had sunk to 
13 inches 11 lines, and the same philosopher descended into 
the sea in a diving-bell, until the mercurial column rose to 45 
inches ; he consequently has safely experienced a change of 
31 inches of pressure in his own person. 

Limits of the Atmosphere. — A person who has risen in 
a balloon, or on a mountain, to the height of 2-705 miles, 
or 14,282 feet, has passed through one-half of the entire 
weight of the air, and finds his barometer to indicate 
this by standing at 15 inches. The upper limits of the 
atmosphere cannot be accurately determined, but it 'is sup- 
posed from the observations of astronomers to be about 45 
miles high. We may judge, then, how extremely thin or 
rare the upper portions must be, when we have one-half of 



35. Is the pressure of the air constantly the same ? How does 
the barometer show this? It varies how much? Arising from 
what cause ? What common name for the barometer is derived from 
its use ? What other important use is made of the barometer ? 
Whence its use for this purpose ? What observations did Hum- 
boldt make on Chimborazo ? What depth did he reach in the sea ? 
How many inches of pressure has he personally experienced ? How 
high must one ascend in order to pass through half the weight of the 
air ? Where will his barometer then stand * How high is the atmo 
sphere believed to extend? 



WEIGHT AND SPECIFIC GRAVITY. 



33 



its entire weight within less than three miles of the earth's 
surface. 

3. Weight and Specific Gravity. 

36. At every step of research the chemist must appeal to 
his balances. This instrument should possess a beam, in- 
flexible by the weight intended to be used, and should be 
delicately poised on a sharp edge of hardened steel, (called 
the knife-edge,) resting on a plate of agate, mounted on the 
summit of an upright pillar of brass. The beam should be 
so accurately made that it will assume a horizontal position 
when at rest, its index or pointer marking zero, on the small 
scale near the foot of the column. At each end of the beam is 
also a knife-edge supporting the scale-pan, and in a delicate 
balance there is always an adjustment by which, when the 
instrument is not in use, the beam is supported on points inde- 
pendent of the 
delicate knife- 
edge, which 
is thus saved 
from unneces- 
sary wear. — 
A good ba- 
lance will turn 
readily with a 
weight of one- 
thousandth part of a grain, when each arm supports one 
thousand grains. In delicate weighing, a glass case is em- 
ployed to protect the balance from the fluctuations of the 
atmosphere. When accurate results are required with a 
balance whose arms are of unequal length, or which is from 
any cause inaccurate, the method adopted is to weigh the 
substance accurately in each pan, and to take the mean of 
the two weighings, which will give the true weight ; or the 
substance being placed in one pan, is counterpoised accu- 
rately by the addition of shot or bits of foil in the other : it 
is then removed, and its place supplied with known weights 
till the equilibrium is restored. The weights added give the 
weight of the substance. The above figure shows the form 




What do we infer of its rarity in the upper regions ? 36. To 
what instrument does the chemist constantly appeal ? Explain the 
construction of the balance. Its use. 



34 MATTER. 

of a good balance, arranged for taking specific gravities. 
One pan is removed, and a shorter one (b) substituted, from 
which by a silk thread the substance (a) is supported in a 
glass of pure water, as explained in 41. 

•It is always assumed, when the weights of substances are 
stated in books of science, that the operation was performed 
at a given temperature by the thermometer; and 60° of 
Fahrenheit's scale is the point agreed upon, because that is 
about the usual temperature of the air; and if it be higher or 
lower, a corresponding allowance is made, because the bulk, 
and consequently the specific weight of bodies, differ with 
their temperature. This precaution is necessary only when 
we take the specific gravity of bodies, and not their absolute 
weights. 

37. Density. — The density of a body is a direct result of 
the law of gravity as already explained (8), the weight 
of a body being the measure of the force of gravity, which 
is directly proportioned to the quantity of matter. The 
greater the number of particles of a given kind within a given 
space, the greater the density of the body, or in the language 
of common life, the heavier it is. Now as bodies differ 
greatly in this particular, each body is said to have a specific 
gravity , or density, peculiar to itself. 

38. Specific Gravity. — The specific gravity of a body is 
its weight, compared with that of some other body of exactly 
equal volume. We say that lead is heavier than cork ; by 
which we mean, that of equally sized pieces of these sub- 
stances, one is very many times heavier than the other ; that 
is, there is very much more matter in the one than in the other 
under equal dimensions. As a difference in specific gravity 
in bodies is found to be accompanied by other important dif- 
ferences, we will give an account of the methods of deter- 
mining this character in liquids, solids, and in gases. 

39. Standards of Specific Gravity. — Pure water at a 
temperature of 60° is the substance which has been adopted 
as a standard of comparison for the specific gravity of all 
solid and liquid substances ; while the dry atmospheric 

37. What is density? What law is it the result of? (8.) The 
density of a body, then, is the measure of what force ? What is the 
density peculiar to each sort of matter called ? 38. Define Specific 
Gravity. What is meant when we say that one body is heavier than 
another ? What is said of the importance of specific gravity ? 39. 
Name the standard adopted for comparison of specific gravity ? 



WEIGHT AND SPECIFIC GRAVITY. 



35 



air at 60° of Fahrenheit and 30 inches of the barometer is 
the standard assumed for all gases and vapors. Thus calling 
water 1, lead will be 1 1*445, or lead is nearly eleven and a half 
times as heavy as water. Cork is lighter -than water, and 
must be expressed by a fractional number. Oil of vitriol 
(sulphuric acid) has a specific gravity of 1-847 when pure, 
or nearly twice as much as water. A pint measure of this 
dense liquid would weigh nearly twice as much as a similar 
measure of water ; while a pint of quicksilver would weigh 
thirteen and a half times as much as a pint of water, and a 
like measure of alcohol only about three-quarters as much, 
(0-794 being the specific gravity of alcohol.) We see now 
the necessity of knowing accurately the temperature of 
substances compared, at the time of weighing, as their bulk 
increases materially with every increase of temperature, and 
their specific gravity consequently diminishes. 

40. Specific Gravity of Liquids. — To measure the spe- 
cific gravity of liquids accurately, a small thin glass bottle 
is required, which holds a known weight of pure water at 
60° when accurately filled. One thousand grains is a con- 
venient quantity for comparison ; but a smaller quantity is 
often more convenient, when we have but little of a substance, 
although it then requires a simple calculation to reduce it to 
the standard. The accompanying figure a shows such a 
bottle. To its neck a glass stopper is 
adapted, by^grinding, which is perfo- 
^ rated by a small hole. 
The weight of the bot- 
tle is counterpoised by 
a small mass of lead, 
which is easily cut by 
a knife to the exact 
weight. This coun- 
terpoise is carefully 
preserved for this pur- 
a pose. The bottle is 

now ready for use ; it is filled with the 
fluid under examination, the stopper is 
carefully introduced, and the excess of the liquid gushes out 





Of solids and fluids. Also for gases and vapors. Mention the ex- 
amples given in the text. 40. Explain the method of finding the 
specific gravity of fluids, and the apparatus figured in this section. 



36 



MATTER. 



through the small orifice. The exterior of the bottle is wiped 
dry, and its weight, when thus filled, is ascertained ; and if 
the bottle is graduated to 1000 grains of pure water at 60°, 
the weight obtained is the specific gravity. For instance, if 
the fluid is pure ether, the 1000 gr. bottle, when filled, would 
weigh only 720 grains, and *720 is the specific gravity of 
ether. As, however, it may not be always convenient to 
procure a thousand-grain bottle, any glass phial may be 
converted into one, which will answer the purpose very well. 
Suppose it to contain 376 grains of pure water: then, as 
376 : 1000, so is the weight obtained to the specific gravity 
of the fluid. A little bottle like the annexed cut (6) answers 
the same purpose, although in a less accurate manner than 
that with the perforated stopper. Its neck is quite narrow, 
and the lines marked on it show the upper and lower surfaces 
of the liquid in the neck. The quantity of pure water which 
it holds at this point is learned from previous trial. 

41. Specific Gravity of Solids. — The determination of 
the specific gravity of solids is founded on the theorem first 
proved by Archimedes, that when a solid body is immersed 
in water, it loses a portion of its weight exactly equal to 
the weight of the water displaced. The 
story in which it is stated that this philosopher 
detected the fraud of King Hiero's goldsmith, 
in furnishing to the monarch, as a crown of 
pure gold, one made of a debased metal, is 
a good example of the practical value of this 
theorem. In fact, plunging an irregular solid 
into water, is the only mode by which we can 
easily and accurately measure the precise bulk 
of the body as compared with an equal bulk of 
water. For convenience in taking the specific 
gravities of solids, a small scale-pan is hung to 
one arm of the balance, (as shown in 36,) 
and the instrument brought to a perfect equi- 
librium. A hook is attached to the lower sur- 
face of this pan, for suspending a thread. It is 
required to take the specific gravity of the mineral quartz. 

If the bottle holds more than 1000 grains, what course is adopted ? 
41. On what is the method for the specific gravity of solids founded ? 
State this theorem in precise terms. What anecdote is mentioned 
of Archimedes ? How do we proceed in taking the specific gravity 
of a solid ? Why does the specimen weigh less in water ? 




WEIGHT AND SPECIFIC GRAVITY. 37 

The specimen is attached by a filament of raw silk, or a fine 
hair, with a noose at the end, to the hook, and the actual 
weight of the mass hanging in the air accurately determined. 
But, in order to have its weight as compared with water, 
we must know precisely how much a mass of water will 
weigh, which is just equal in bulk to the specimen. Now if 
we suspend it as it hangs from the scale-beam in a vessel of 
pure water, we shall displace just such a quantity of water 
as corresponds with the bulk of the crystals, and no more ; 
the water will buoy up the specimen by a weight just equal 
to a like bulk of water : in other words, the specimen will 
weigh less in water than it did in air ; and we must diminish 
the weight on the other side of the beam, to correspond with 
this loss of weight. If we now subtract from the weight in 
air, that which we have found to be its weight in water, the 
difference will evidently give us the weight of a bulk of water 
exactly equal to the bulk of our specimen. As water is 
the standard of comparison which has been adopted for spe- 
cific gravity, if we divide the actual weight of the substance 
in air by the weight of an equal bulk of water, we shall have 
the specific gravity sought. 

42. We deduce the following rule for determining specific 
gravity. Subtract the weight in water from the weight in 
air, divide the weight in air by the difference thus. found, 
and the quotient will be the specif c gravity. A single 
example may serve to impress this simple but important 
subject on the mind of the learner : we find on trial that the 

Weight of the substance in air, is 357-95 grs. 

Weight of the substance in water, " 239-41 " 

Difference, 118-54 " 

35795 

ilS54 = ^' 01 8 P ec ifi c gravity.* 

How much less does it weigh ? 42. State the rule which is given 
for finding the specific gravity. Give an example on the black-board. 
[Note.) Explain the principles and use of Nicholson's Araeometer. 
Srive an example of its use. 



* Nicholson's Arcsometer. — A cheap and convenient substitute for 
'he balance is found in a little instrument represented in the annexed 
rut, and called Nicholson's Areometer, which we will briefly de- 
scribe, v is a metallic ball or float having a descending hook, to 
tfhich is hung a little weighted pan / to hold the substance which is 
4 



38 



MATTER. 



43. Substances which are lighter than water can have 
their specific gravity taken, by attaching to them any con- 
venient bit of metal which will sink them ; the weight of the 
substance is taken in air, and then the united weight, after 
attaching the piece of metal. The weight in water of both 
united is now taken, and the light body being detached, the 
weighing is repeated on the metallic body. 

44. For this purpose we may also take some liquid in 
which the light body will just float, and then determine the 
specific gravity of the fluid by the bottle, (40,) which will give 
us at once the specific gravity of the solid. Thus, if we put 
a lump of wax into water, it will float above the surface ; but 

43. How can we take the specific gravity of substances lighter 
than water ? 44. Explain another method by the use of the speci- 
fic gravity bottle, and its principle. 



weighed in water ; the wire stem / supports a cup c. 
A mark t on the stem shows the point at which the 
whole apparatus will float in a tall vessel of water 
when a certain known weight (called the balance 
weight) is put in the cup c. The specimen under 
examination must not exceed in weight the balance- 
weight, this being the limit of the instrument. Sup- 
pose the limit to be 100 grains. To find by this in- 
strument the specific gravity of a substance, place it 
on c, and add weights till the instrument sinks to the 
mark t ; the added weight being subtracted from 
100, gives the weight of the specimen in air. Now 
place the specimen in the pan I, and again add 
weights to c As much more weight on c will now 
be required as corresponds to the weight of a bulk 
of water equal to the specimen, which it must be 

remembered is buoyed up by a power just equal to such weight. 

The difference of weight thus found will be the divisor of the 

weight of the specimen, and the quotient will be the specific gravity 

sought. 

This instrument is generally made of brass or tin-plate, but may 

be more elegantly made of glass. 

For example, put the specimen in 

Balance weight = 100-00 

Weights added to sink instrument to t — 22-57 grs. 

Weight of specimen in air = 77-43 

Specimen placed in lower pan requires ad- 
ditional weights = 35-43 




7743 



35.43 — 22*57= 12-86, the weight of a like bulk of water ; then ^86 
= 6-02, the specific gravity sought. 



WEIGHT AND SPECIFIC GRAVITY. 39 

in pure alcohol it will sink. If we dilute the alcohol by small 
doses of water, we shall soon find a point when the wax will 
just float, or rise and sink indifferently. The alcohol at this 
state of dilution has the same specific gravity as the wax, and 
this we find by the specific gravity bottle to be about 0*9. 

45. If a substance is in powder or in small grains, its 
specific gravity is found by taking a known weight of it, and 
having introduced it into the specific gravity bottle for fluids, 
to fill it with pure water and weigh : the weight of the sub- 
stance being deducted from the weight of the whole contents 
of the bottle, the difference between the sum thus obtained 
and the weight of the water which the bottle alone will hold, 
corresponds with the difference between the weight of the sub- 
stance in air and water. For instance, we introduce 100 
grains of a powdered mineral into a specific gravity bottle, 
holding 1000 grains of pure water, and fill the remaining 
space with water at 60°. We might expect that we should 
have a weight of 1100 grains, but find only 1059, the place 
of some of the water being occupied by the powder introduced. 

The bottle holds, 1000 grains. 

Substance introduced weighs, 100 " 

1100 
Weight found, 1059 

Difference, 41 

100 

-jl sss 2-044, the specific gravity sought. 

46. If the substance is soluble in water, we must employ 
a fluid of known specific gravity, in which it is not soluble. 
For instance, sugar cannot be weighed in water, but in abso- 
lute or pure alcohol* it can. The specific gravity being 
determined in a fluid whose specific gravity, as compared 
with water, is known, it is easy by a simple proportion to tell 
the specific gravity of the solid. 

47. The Hydrometer* is an instrument of great use in 
determining the specific gravity of liquids without a balance. 

45. If the substance is in powder, how do we proceed ? Give the 
example named in the text on the black-board. 46. If the sub- 
stance is soluble in water, how do we proceed ? 47. What is the 
hydrometer ? 

* From the Greek ktulor, water, and victron, measure. 



40 



MATTER. 



It is simply a glass tube with a bulb blown on one end of it, 
containing a few shot to counterbalance the instrument, while 
a scale of equal parts is made of paper and introduced into 
the open end, which is then tightly sealed. This scale indi- 
cates the points to which the stem sinks when immersed in 
fluids of different densities. The fluid for convenience is 
placed in a tube or narrow jar ; the more dense the fluid, the 
less quantity will the hydrometer displace, while in a lighter 
fluid it will sink deeper. The zero point of the scale is 
always placed where the instrument will rest in pure water, 
after which the graduation is effected on a variety of arbi- 
trary scales, all of which can however be referred to the true 
specific gravity, by calculation. The 
scales of these instruments read either up 
or down, according as the fluid to be 
measured is either heavier or lighter than 
water. In case of alcohol, (it being lighter 
than water,) the graduation of the hy- 
drometer is made to indicate the number 
of parts of pure alcohol in a hundred 
parts of the liquid, absolute alcohol being 
100, and water 0. The hydrometers of 
Baume (a French maker) are much used 
in the arts. These instruments are of the 
greatest service to the manufacturer, and 
£d____Jfc^ when carefully made are sufficiently ac- 
^= ^ ^ curate for most purposes of the laboratory. 
They should always be proved by comparison with the 
balance before they are accepted as standards. For many 
purposes they are made of brass or ivory, as well as of glass. 
48. Little balloons or bulbs of glass are frequently em- 
ployed to find, in a rough way, the density of 
fluids. When several of them are thrown in a 
fluid of known density, some will sink, some rise 
even with the surface, and others will just float. 
Those which just float are taken, and being marked, 
(as in the figure, with the density of the liquid 




Explain its principal use. What is the zero of its scale ? In case of 
alcohol how is it graduated ? How do we find the true specific gravity 
from the arbitrary scale ? 48. What are specific gravity bulbs ? 
How are they used ? Mention the case in which they are most 
useful. 



SOURCES AND PROPERTIES OF LIGHT. 



41 



which they represent,) are then used to determine the spe- 
cific gravity of liquids of unknown density. They are called 
specific gravity bulbs, and are of great service in ascertaining 
the density of gases reduced to a liquid by pressure in glass 
tubes, when, from the circumstances of the experiment, all 
the usual modes of ascertaining specific gravity are inappli- 
cable. The method described in 44 for finding the gravity 
of light substances, involves the same principle as that here 
given. 

49. Specific Gravity of Gases. — It remains only, under 
this heYtd, to speak of the modes used for determining the 
specific gravity of gas^s anjsjl vipers. For this purpose a 
globe, or other conveniently formed glass vessel, holding a 
known quantity by measure, (usually 100 cubic inches) is 
carefully freed from air or moisture, by the air-pump or 
exhausting syringe, and is then filled with the gas 
or vapor in question, and at 60° Fahrenheit, and 
30 inches of the barometer, (32), and weighed ; the 
weight of the apparatus filled with common air 
being previously known, the difference enables the 
experimenter to make a direct comparison. The an- 
nexed figure shows an apparatus for this purpose ; 
the globe (b) is provided with a stop-cock, (e), and 
fitted by a screw to the air-jar (a.) The jar is 
graduated so that the quantity of air or other gas 
entering may be known from the rise of the water 
in (a.) It is thus found that 100 cubic inches of 
pure dry air weigh 31*0117 grains, while the same 
quantity of hydrogen gas weighs only 2*14 grains, 
being about fourteen times lighter than air. 




*vw * "• LIGHT - 

50, The physical phenomena of light properly belong to 
the science of Optics, a branch of -natural philosophy not 
necessarily connected with chemistry. A knowledge of 
some of the laws of light is, however, required of the chemi- 
cal student, and the progress of discovery daily shows us 



What previous case involves the principle of the bulbs ? 49. How 
do we find the specific gravity of gases ? Explain the apparatus 
used. How much do we thus find the air to weigh ? 50. To what 
branch of science does light properly belong ? What is said of its 
chemical importance ? 
4 # 



42 LIGHT. 

some new connection between the phenomena of light and 
chemical action. 

51. Sources and Nature of Light. — The sun is the great 
source of light, although we can show many minor and arti- 
ficial sources. Of the real nature of light we know nothing. 
Sir Isaac Newton argued that it was a material emanation 
from the sun and other luminous bodies, consisting of parti- 
cles so attenuated as to be wholly imponderable to our means 
of estimating weight, and having the greatest imaginable re- 
pulsion to each other. These particles, by his theory, are 
supposed to be sent forth in straight lines, in all directions, 
from every luminous body, and which, falling on the delicate 
nerves of the eye, produce the sense of vision. This is 
called the Newtonian or corpuscular theory of light. It is 
not now generally believed to be true, but the language of 
optical science is formed on the supposition of its correctness. 
The other view or theory of light, which is now generally 
accepted, is called the wave or undulatory theory. It is 
known that sound is conveyed through the air by a series of 
vibrations or waves, pulsating regularly in alf directions, 
from the original source of the sound. In the same manner 
it is believed that light is conveyed to the eye by a series of 
unending and inconceivably rapid pulsations or undulations, 
imparted from the source of light to a very rare or attenuated 
medium, which is supposed to fill all space. This medium 
is called the luminiferous ether (15.) However difficult it 
may be to form any just comprehension of the ultimate or 
real nature of light, we do know many things about its 
properties, some of which may be enumerated, and briefly 
explained. 

52. Properties of light. — 1st. Light is sert forth in rays 
in all directions from all luminous bodies. 2d. Bodies not 
themselves luminous become visible by the light falling on 
them from other luminous bodies. 3d. The light which pro- 
ceeds from all bodies has the color of the body from which 
it comes, although the sun sends forth only white light. 4th. 

51. Name the great source of light ? What do we know of its 
nature ? Give the theory of Newton. What is this theory com- 
monly called ? What is said of its probability and truth ? What 
is the now accepted doctrine ? Explain what is meant by the un- 
dulatory theory. What is it which is supposed to undulate ? What 
name is given to this medium ? 52. State what is known of light. 
1st. Its ravs. 2d. Of its luminousness. 3d. Of its color. 



REFLECTION. 43 

Light consists of separate parts independent of each other. 
5th. Rays of light proceed in straight lines. 6th. Light 
moves with a wonderful velocity, which has been computed by 
astronomical observations to be at least one hundred and 
ninety-five thousands of miles in a second of time. This 
velocity is so wonderful as to surpass our comprehension. 
Herschel says of it, that a wink of the eye, or a single motion 
of the leg of a swift runner, or flap of the wing of the swiftest 
bird, occupies more time than the passage of a ray of light 
around the globe. A- cannon-ball at its utmost speed would 
require at least seventeen years to reach the sun, while light 
comes over the same distance in about eight minutes. 

53. When a ray of light falls on the surface of any body, 
several things may happen. 1st. It may be absorbed and 
disappear altogether, as is the case when it falls on a black 
and dull surface. 2d. It may be nearly all reflected, as from 
some polished surfaces. 3d. It may pass through or be 
transmitted ; and 4th. It may be partly absorbed, partly re- 
flected, and partly transmitted. Bodies are said to be opake 
when they intercept all light, and transparent when they per- 
mit it to pass through them. But probably no body is either 
perfectly opake or transparent, and we see these properties in 
every possible degree of difference. Metals, which are 
among the most opake bodies, become partly transparent 
when made very thin, as may be seen in gold-leaf on glass, 
which transmits a greenish purple light, and in quicksilver, 
which gives by transmitted light a blue color slightly tinged 
with purple. To protect pictures formed by the daguerreo- 
type process, they are covered with a film of gold or copper, 
so thin as not to injure the impression, and yet it effectually 
prevents its removal by the touch. On the other hand, glass 
and all other transparent bodies stop the progress of more or 
less light. 

54. Refection. — Light is reflected according to a very 



4th. Of its parts. 5th. Of its course. 6th. Of its velocity. Il- 
lustrate this by the examples named by Herschel. What is said 
of the speed of a cannon-ball ? 53. State what becomes of a ray 
of light falling on any surface. 1st. On a dull surface. 2d. On a 
polished surface. 3d. On a transparent. 4th. What else may hap- 
pen ? What is a transparent body ? What is an opake one? Are 
these qualities ever perfect ? What is said of the opacity of gold 
and quicksilver ? Of the gold and copper in the daguerreotype ? 
54. State the law of reflection. 



u 



LIGHT. 




simple law. In the annexed figure, if the ray of light fall 
from P' to P, it is thrown directly- 
back to P' ; for this reason a per- 
son looking into a common mirror, 
sees himself correctly, but his im- 
age appears to be as far behind the 
mirror as he is in front of it. If 
the ray fall from R to P, it will be 
reflected to R', and if from r, then it will go in the line r', and 
so for any other point. If we measure the angles RPP' and 
P' P R', we shall find them equal to each other, and so also 
the angles rPP' and P' P r'. These angles are called re- 
spectively the angles of incidence and refection. We there- 
fore state that the angle of incidence is equal to the angle 
of reflection, which is the law of simple reflection. This 
law is as true of curved surfaces as it is of planes ; for a 
curved surface (like a concave metallic mirror) is considered 
as made up of an infinite number of small planes. 

55. Simple Refraction. — If a ray of light falls perpendi- 
cularly on any transparent or uncrystallized surface, as glass 
or water, it is partly reflected, partly scattered in all direc- 
tions, (which part renders the object visible,) and partly 
transmitted in the same direction from which it comes. If, 
however, the light come in any other than a perpendicular or 
vertical direction, as from R to A, 
on the surface of a thick slip of 
glass, as represented in the figure, 
it will not pass the glass in the line 
R A B, but will be bent or refract- 
ed at A, to C. As it leaves the 
glass at C, it again travels in a di- 
rection parallel to R A, its first 
course. Refraction, then, is the 
change of direction which a ray 
of light suffers on passing from a 
rarer to a denser medium, and the reverse. In passing from 
a rarer to a denser medium, (as from air to glass or water,) 




Draw the diagram on the board and demonstrate it. What is the 
angle of incidence ? What that of reflection ? How does this law 
apply to curved surfaces ? 55. What becomes of a ray of light when 
it falls perpendicularly on a transparent surface ? When obliquely ? 
Demonstrate it on the black-board from the diagram. Give the 
definition of the law of refraction. Which way is the ray bent ? 



AMOUNT OF REFRACTION. 



45 



the ray is bent or refracted towards a line perpendicular to 
that point of the surface on which the light falls, and from a 
denser to a rarer medium the law is reversed. 

A common experiment, in illustration of this law, is to 
place a coin in the bottom of a bowl, so situated that the 
observer cannot see the coin until water is poured into the 
vessel ; the coin then becomes visible, because the ray of 
light passing out of the water from the coin, is bent towards 
the eye. In the same manner, a straight stick thrust into 
water appears bent at an angle where it enters the water. 
^ 56. Amount of Refraction. — The obliquity of the ray to 
the refracting medium, determines the amount of refraction. 
The more obliquely the ray falls on the surface, the greater 
the amount of refraction. A little modification of the last 
figure will make this clear. Let R A be a beam of light 
falling on a refracting medium, it 
is bent as before to R'. If we 
draw a circle about A as a centre, 
and a line a a, from the point a 
where the circle cuts the ray R at 
right angles, to the perpendicular -- 
passing through A, the line a a is 
called the sine of the angle of inci- 
dence ; while the line a' a' is called 
the sine of the angle of refraction. 

If a more oblique ray r, cuts the circle at b, the line b b 
will be longeMhan the line a a, inasmuch as the angle b A a, 
is greater than the angle a A. a. 

The line measuring the obliquity before refraction, when 
the ray passes into a denser medium, is always greater than 
that which measures it after, and is nearly one-third more in 
the case of water. This is called the index of refraction ; 
the refractive power of water is expressed by 1^ or 1-33, 
while common glass with a higher refractive power, has the 
index of refraction li or 1*5, and the diamond 2*239. In 




What two common illustrations of this law are named ? 56. What 
determines the amount of refraction ? Show how this can be demon- 
strated by an alteration of the last figure. What is the line a a 
called ? What is a a, called ? What is said of the line measuring 
the obliquity before refraction and after ? How much greater in the 
case of water? What is it called ? What is the refractive index 
of water ? 



46 



LIGHT. 




the larger works full tables will be found with the refractive 
indices of numerous substances. 

57. Substances of an inflammable nature, or containing 
carbon, and those which are dense, have, as a general thing, 
a higher refracting power than others. Sir Isaac Newton 
observed that the diamond and water had both high refracting 
powers, and he sagaciously foretold the fact, which chemis- 
try has since proved, that both these substances had a com- 
bustible base, or were of an inflammable nature. We now 
know that the diamond is pure carbon, and that water has 
hydrogen, a combustible gas, as one of its constituents. 

, 58. Prism. — In the cases of sim- 
ple refraction just explained the ray, 
after leaving the refracting medium, 
goes on in a course parallel to its 
original direction, because the two sur- 
faces of the medium are parallel. If, however, we employ a tri- 
angular glass prism like the figure, or any other surfaces not 
parallel, the ray will be diverted permanently from its original 
direction after leaving the prism. As already explained, the ray 
R is bent towards a perpendicular to the surface, (which is the 
dotted line,) but on leaving the prism it is by the same law fur- 
ther refracted in the direction R'; and by altering the form of 
the surfaces we may thus send it in almost any direction, as 
in the common multiplying-glass, which gives as many im- 
ages as it has faces, and all in different directions. In this 
way it is that concave metallic mirrors concentrate and convex 
ones disperse a beam of light. 

59. Analysis of Light. — By means of the prism we learn 

that a beam of sun- 
light is not simple 
white light, but a 
compound of seve- 
ral colors of the 
-most vivid tints 
which can be im- 
agined. We are indebted to Sir Isaac Newton for this beau- 




57. What is said of inflammable substances ? What was Newton's 
conjecture about diamonds and water ? What do we now know of 
them ? 58. If the surfaces of the refracting medium are not parallel, 
how is the ray affected ? Explain this by the figure. Give an instance 
of the application. 59. What do we learn by means of the prism ? 
Who discovered this, and what is it called ? 



PRISMATIC COLORS. 



47 



tiful experiment, which is called Newton's Analysis of Light. 
A beam of sunlight from R, in the figure, falling from a 
small circular aperture in the shutter of a darkened room on 
a common triangular prism, is refracted twice, and bent up- 
ward towards the white screen R', placed at some distance 
from the prism, where it forms an oblong colored image, 
composed of seven colors. This image is called the pris- 
matic or solar spectrum. 

The light from flames of all kinds, the oxy-hydrogen 
blowpipe, and the electric spark, or galvanic light/ is also 
compound in its nature, like that of the sun and other celes- 
tial bodies. 
hF 60. Prismatic Colors. — The colors of the solar spectrum 
are in the following order, upwards : red, orange, yellow, 
green, blue, indigo, violet. These colors are of very dif- 
ferent refrangibility, and for this reason are presented in a 
broad surface, the red being the least refracted, and the violet 
the most. The seven colors of Newton, it is believed, are, 
really composed of the three primitive ones, red, yellow, and 
blue. This idea is well expressed in the following diagram. 
The three primitive 
colors each attain 
their greatest in- 
tensity in the spec- 
trum at the points 
marked at the sum- 
mit of the curves ; 
while the four other 
colors, violet, in/di- 
go, green, and orange, are the result of a mixture, in the 
spectrum, of the other three. A portion of proper white light 
is also found in all parts of the spectrum, which cannot be 
separated by refraction. We may hence infer that there is 
a portion of each color in every part of the spectrum, but 
that each is most intense at the points where it appears 



RED. SOLAR SPECTRUM. 




Explain from the figure how this is done. Is the image on the screen 
circular ? What name is given to the image ? How many colors 
are in it ? Why do we say the light is analyzed ? Is light from 
other sources compound ? 60. Give the order of the colors in the 
solar spectrum. Why are these colors separated to different parts 
of the spectrum ? Which is most bent, and which least ? What 
are the three primitive colors ? Explain the diagram, and how the 
three united form the seven. Is each color pure, or mixed with 
some white light ? When most pure ? 



48 LIGHT. 

strongest. The light is most intense in the yellow portion, 
and fades toward each end of the spectrum. 

Sir John Herschel has detected rays of greater refrangi- 
bility than the violet of the spectrum, which have a lavender 
color. They have this color after concentration, and are 
therefore not merely, as might be supposed, dilute violet rays. 

If the spectrum is formed by a beam of light passing 
through a slit not over -^th of an inch in width, the image 
will be crossed by a number of dark lines, which always 
appear in the same relative position. These are called the 
fixed lines of the spectrum, and are much referred to as 
boundary lines in optical descriptions. These lines can be 
transferred to the sensitive papers used in photography. 

61. Natural Color of Bodies. — The color of bodies in 
nature are due to the fact that their surfaces absorb all the 
light, except the color we recognise as belonging to each 
object. This property is to be ascribed to some cause in- 
herent in the nature of the substances. 

62. Double Refraction. — The refraction which we have 
just considered, belongs to all bodies which permit the pass- 
age of light. But in most crystalline substances, and all 
bodies having any regular internal structure, such as bone, 
shell, &c, there is another sort of refraction. By looking 
through such bodies in certain positions, two objects are seen 
instead of one, one by the ordinary, and the other by an ex- 
traordinary ray. 

This phenomenon is called Double refraction, and is best 
seen in the mineral called calc spar, or Iceland spar, which, 
when pure, is colorless and transparent, and breaks into regular 
rhombs, with brilliant faces. If a rhomb of this mineral be 
laid over a black line, we see a double image, as if there were 
in reality two lines.* This direction of the ray is owing to 

What is lavender light ? Describe the lines observed in the spec- 
trum. 61. Give the cause of the color of natural bodies. 62. How 
generally is simple refraction found in transparent bodies ? What 
bodies have another sort of refraction ? What is seen on looking through 
such bodies ? What is this property called ? In what best seen ? 

j, * A sharp line like p q, when seen 
through a rhomb of calc spar in the direc- 
tion of the ray R r, will seem to be dou- 
ble, a second parallel line m n, being 
seen at a short distance from it, and 
the dot o, will have its fellow e. In this 
case the light is represented as coming 
from R to r, and passing through the crys- 




POLARIZATION. 



the interior crystalline structure of the mineral. Of the two 
beams into which the light is divided, one obeys the law of 
refraction already explained, while the other pursues an en- 
tirely different course. One is called the ordinary, and the 
other the extraordinary ray. 

63. Polarization. — The light which has passed one crys- 
tal of Iceland spar by extraordinary refraction, is no longer 
affected like common light. If we attempt to pass it through 
another crystal of the same substance, there will be no fur- 
ther subdivision, and only a greater separation of the two 
beams. 

This peculiar physical change is called polarization, as 
the light is supposed to assume a polar condition. Many 
other mineral substances also polarize light when cut into 
thin plates. The mineral called tourmaline has this property 
in a remarkable degree. The internal structure of this 
mineral is such, that a ray of light can pass through thin 
plates of it in one direction, but not in another; as, for illus- 
tration, a thin blade may pass between the wires of a cage if 
held parallel to the interstices, but will of course be arrested 
if turned at right angles to them. 

In the annexed 
figure we have two 
thin plates of tour- 
maline placed par- r_ 
allel to each other 
in the same direc- 
tion. A ray of 
light passes through 
both in the direction of JR R', and apparently suffers no 





What is this property owing to ? Explain the figure in the note, 
on the board. 63. How is the ray which has passed one crystal of 
calc spar affected by another ? What is this change called ? In what 
else is it seen ? How is it illustrated ? Explain the figures of the 
tourmaline plates. 



tal, it is split and emerges in two beams at e and o. The same 
effect would be produced if the light fell so as to strike any part of the 
imaginary plane ACBD, which diagonally divides the crystal, and is 
called its principal section. The axis or line drawn from A to B, is 
contained in this plane. But if we look through the crystal in a di- 
rection parallel to this plane (ACBD) there is only simple refrac- 
tion, and only one line is seen. 
5 




50 LIGHT. 

change : if however, these plates are so placed as to cross 
each other at right angles, as in the second figure, the ray of 
light is totally extinguished ; and four such points may be 
found in revolving one of the plates about the ray as an axis. 

64. Light is also polarized when passed obliquely through 
a bundle of plates of thin glass, or mica, 
arranged as in the figure. The reflection of 
light from the surface of various substances is 
also productive of polarization, at an angle which 
is peculiar to each substance, and hence called 
the angle of polarization. This angle on glass 
is found to be 56°48'. The phenomena of 
polarized light are among the most attractive 
and important in the science of optics, but 
their study would lead us away from our pre- 

*' sent object. 

65. Chemical Rays. — Besides the rays of light in the so- 
lar spectrum which we have already noticed, and the rays of 
heat which we shall presently consider, there is still another 
class of rays, which, while they have a greater refrangibility 
than the violet, are also found by the delicate experiments of 
Herschel, to be present in every part of the solar spectrum : 
they have been sometimes called the chemical rays, from the 
powerful effect which they produce in chemical combinations. 
They act in a manner altogether independent of the rays of 
heat. Chlorine and hydrogen gases are made to combine by 
them with explosive energy, while in diffuse light the union 
of these gases is slow and quiet. 

Many metallic salts are changed to a darker color by their 
action, as the chlorid and iodid of silver, facts which have 
been beautifully applied in the arts of photography by sensi- 
tive papers, and of the daguerreotype. The last depends on 
the sensitiveness of the iodid of silver to the action of the 
chemical or more luminous rays of the sun. This power in 
the non-luminous rays has been variously designated by the 
terms actinism, tithonicity, and energia. 

66. The accompanying diagram will enable the student to 



64. How else is light polarized ? How by reflection ? What is 
the angle called ? What is it for glass ? 65. What other class of 
rays is named? How do they act? Give examples of their effects. 
What arts are dependent on the chemical rays ? What has this 
power been called ? 



CHEMICAL RAYS. 



51 



obtain clearer views of our present knowledge in relation to 
this interesting subject, which has already made so many- 
splendid presents to the arts. From A to B, we have the 
solar spectrum with the colors in the same order as already 
described, (60.) The greatest chemical power is at the vio- 
let, and the greatest heat at the red ray. At b another red ray 
is discovered, and at a is the lavender light. The luminous 
effects are shown by the curved line C, the maximum of light 
being found at the yellow ray. The point of greatest heat is 
at 2>, beyond the red ray, and 
it gradually declines to the 
violet end, where it is entirely 
wanting, the other limit of heat 
being at c. The chemical 
powers are greatest about E, LAVEXDERj 
in the limits of the violet, and 
gradually extend to d, where 
they are lost. They disap- 
pear also entirely at C, the blue, . 
yellow ray, which is neutral in GREEN > 
this respect, attain another TELL0W > 
point of considerable power at 
F, in the red ray, which gives 
its own color to photographic 
pictures; and ceases entirely 
at e. The points D, C, E, 
therefore, represent respective- 
ly the three distinct phenomena 
of Heat, Light, and Chemical 
Power. This last is believed to be quite independent of the 
other powers ; for all light may be removed from the spec- 
trum by passing it through blue solutions, and yet the chemi- 
cal power remains unaltered. 

67. Spectral Impressions. — In connection with the chemi- 
cal properties of light, we mention the curious fact that bodies 
have the power of impressing their images or pictures on each 
other in the dark, or on plates of polished metal and glass, 
in such a manner that these become at once visible, if the 
bright surface be breathed on or exposed to the vapor of 



VIOLET, 
IKDIGO, 



ORANGE, 
RED, 



EXTREME RED 




Explain the diagram illustrating the points of greatest light, heat, 
and chemical action. What is found at JFon the scale ? Is the chem- 
ical power independent of light ? 67. What are spectral impressions ? 



52 LIGHT. 

mercury, as in the daguerreotype. If a coin or medal is 
placed on a finely polished surface of sheet-copper or silver, 
and be left in a perfectly dark place for a few hours, (parti 
cularly if the plate has been warmed,) it will be found that 
on breathing upon or mercurializing the metallic surface, an 
image of the object will at once be brought out, and can be 
renewed in the same manner indefinitely. It is supposed 
that this efFect is owing to an invisible influence, passing be- 
tween the two objects, and producing a change in the condition 
of the surface, or the arrangement of its particles. Engrav- 
ings can be permanently copied in this way, and many curi- 
ous and instructive experiments performed, which our space 
will not permit us to describe. 

68. Phosphorescence is a property possessed by some 
bodies of emitting a feeble light, often at ordinary tempera- 
tures. The diamond and some other substances, after being ex- 
posed to the rays of the sun, will emit light for some time in the 
dark. Fluor-spar, feld-spar, and some other minerals, give out 
a fine light of varied hues, when gently heated or scratched. 
Oyster-shells which have been calcined with lime and exposed 
to the sun-light, will shine in a dark place for a considerable 
time afterwards. The glow-worm, the fire-fly, rotten wood, 
decaying fish, and various marine animals, possess the same 
property in a greater or less degree. 

This and similar facts, have been made the basis of an 
argument by Dr. Draper, to sustain the opinion that there is, 
in addition to light, heat, and electricity, & fourth imponderable 
agent. 

This brief outline of the history of light, must impress the 
belief that this agent holds a most important place in main- 
taining the physical welfare of our planet. 

Plants, by aid especially of the yellow rays, transform the 
inorganic constituents of matter into living and growing or- 
ganisms, which appropriate their food, decompose and recom- 
pose various compounds in a manner which the chemist can 
never hope to imitate. j 

How are they produced ? 68. What is phosphorescence ? What 
substances possess it ? What opinion has been based on such facts ? 
What is said of the importance of light ? How are fluids affected by 
it ? Which ray is effectual in vegetation ? 



SOURCES OF HEAT. 53 



III. HEAT. 



69. All our knowledge of heat is confined to its effects. 
We experience a sensation on coming near to, or touching 
other bodies, which we call heat or cold, according as they 
have a higher or lower temperature than ourselves. This is 
the common use of the word. In chemical language, we 
mean by heat, the unknown cause of the effects produced by 
it on bodies, and not the sensation. We are as ignorant of 
the real nature of heat as we are of that of light. It is often 
called an imponderable agent, as has been before mentioned, 
because we can find no increase of weight in bodies by heat- 
ing them, nor any decrease in weight by cooling them. The 
changes which heat has power to work on matter are wonder- 
ful; and as it is one of the most important of chemical agents, 
we shall be well employed in the study of its phenomena. 

Without pausing, therefore, to consider any of the inge- 
nious theories which have been proposed regarding the nature 
of heat and its relations to matter, we will proceed to con- 
sider its sources and effects. 

70. Sources of Heat. — 1st. The sun is the great source 
of heat. His rays alone make the earth inhabitable ; with- 
out them, this world would be only a barren waste, and its 
waters would be as solid and unalterable as granite. All the 
combustible material on or in the earth, would not supply the 
want of the sun for a single day. 

2d. Combustion is another source of heat. Our fires give 
us warmth, because the combustible part of the fuel takes on 
a new form of existence, combining chemically with one 
portion of the atmosphere, and evolving heat. This 
source of heat, then, is due to a change of state in bodies. 
The same cause we shall also see, further on, (111,) may 
sometimes be a source of cold, that is, of a diminution of 
heat. This source of heat is entirely limited by the amount 
of the substances suffering change, and ceases when the change 
is complete. 



69. What do we know of the nature of heat ? Distinguish be- 
tween its nature and our sensations. 70. Name the first source of heat. 
The 2d. Why does the fire warm us ? What limits this source of 
heat? 

5* 



54 HEAT. 

3d. Friction is a third source of heat. Heat is generated 
by friction to an indefinite amount, as in the rubbing together 
of two limbs in a forest, moved by violent winds, by which 
it is said that so much heat has been excited as to set fire to 
large tracts of timber-land. Savage nations, by rubbing two 
sticks violently together, are accustomed to produce fire. 
Large plates of iron have been made to move slowly over 
each other, by water-power, thus producing heat enough to 
warm extensive buildings. The water beneath which cannon 
are bored becomes very hot, from the friction of the borer 
against the metal which it cuts. The principal thing to be 
remarked in reference to this source of heat is, that it seems 
to be without limit, so long as motion is continued ; and that 
the substances used to produce friction do not necessarily 
suffer any permanent change of state. The evolution of heat 
goes on, the substances acted on neither increasing nor dimin- 
ishing in quantity, while the body retains its chemical pro- 
perties unaltered. 

4th. A fourth source is Electricity, and it is probably 
very closely allied to the second. The spark from the elec- 
trical machine, the galvanic current, and the lightning, are 
alike sources of heat. 

We might also mention the warmth of our own bodies, 
and the whole animal world, as another source of heat ; but 
it seems more than probable that animal heat is only the 
result of chemical changes going on in the process of respi- 
ration, and the other functions of the body, and as such be- 
longs to the second source, already mentioned. 

5th. Geology teaches us that the interior of the earth x§ 
in a state of intense ignition, amounting at times to fluidity, 
as is proved 1 by the eruptions of lava from active volcanoes. 
All the excavations for mines and artesian* wells which have 
been made have shown, that as we descend, the temperature 
of the earth constantly increases, after we have passed below 

What is said of friction ? Give examples of heat thus produced. 
What is said of electricity and animal heat ? What has geology 
taught? State the facts. Does heat from these various sources 
differ in kind ? 



'Artesian wells are borings made with an auger, usually to a 
great depth, and are so called from the province of Artois in France, 
where they were first made. 



EXPANSION. 55 

the influence of the atmosphere. This increase amounts to 
about 1° of Fahrenheit's thermometer for every 40 or 45 feet 
of descent. The celebrated well of Grenelle, at Paris, (which 
is an artesian boring,) is 1794 feet deep, and its temperature 
is 82°, which is 31° above the mean temperature of Paris; 
and the well at Mondorf, in the Duchy of Luxemburg, is 
2200 feet deep, and the water rises with a temperature of 95° 
Fahrenheit. This increase of temperature, if continued at 
the same rate, would give us boiling water at about two miles 
from the surface. At ten miles, all solid substances would 
become intensely red ; and at thirty or forty, all known solids 
would be in a state of fusion. No doubt the central heat 
of the earth, escaping by insensible degrees to the surface, 
has had an important influence on its condition. 

From whatever source heat may be derived, its effects on 
matter are the same, and we will first consider one of its most 
general powers, namely, — 



1. Expansion, — The effect of Heat in altering the dimen- 
sions of Bodies. 

• 

71. Heat has been called the antagonist of attraction: 
while the latter power acts to bind together the particles of 
matter, heat tends to separate them. We see about us mat- 
ter in the different forms of solids, liquids, and gases or vapors. 
Water presents a familiar instance of a substance known to 
us in all three of these states ; as a solid in ice, a liquid at 
common temperatures, and an invisible vapor at higher tem- 
peratures. The sole cause, so far as we know, of this change 
of state in water, is variation of temperature. 

72. We have before seen (26) the remarkable power of 
elasticity in expanding air and other gases. Heat produces 
expansion in all bodies, even the most firm ; and this is so 
powerful as to set at defiance all attempts to restrain it. 

73. To show the expansion of a solid, a bar of metal 



What is said of the well at Grenelle ? What would happen if the 
ratio of increase of temperature continued the same ? 71. Of what 
is heat the antagonist force ? Illustrate this. 72. What power of 
heat do we now consider ? 



56 



HEAT. 



f ■""■■"'"imiiiilillUllllllllllJ 



f% 



is provided with a handle, (see an- 
nexed figure,) which at ordinary tem- 
peratures, exactly fits a gauge; on 
heating this over a spirit-lamp, or 
by plunging it into hot water, it will 
be so much swelled (expanded) in 
all its dimensions, as no longer to 
enter the gauge. On cooling it with 
ice, it will again not only enter freely, 
but with room to spare. The same 
fact is shown by a small cannon-ball, 
to which, when cold, a ring with a 

handle will exactly fit, but on heating the ball in the fire, the 

ring will no longer encircle it. 

74. The expansion of a fluid may be shown by filling 
the bulb of a large tube a with colored 
fluid to a mark on the stem. On plung- 

Iing the bulb into hot water, the fluid is 
seen to rise rapidly in the stem. If it 
be cooled by a mixture of ice and water, 
it is seen to sink considerably below the 
line. A similar bulb 6, filled with air, 
and having its lower end under water, 
is arranged as in the figure to show the 
^/B£jt expansion of air by heat. The warmth 
A 3BS °f tne nan d applied to the naked ball 

V jjp BBSS wu "l b e sufficient to cause bubbles of air 

v - to escape from the open end through the 

water, and on removing the hand, the 
contraction of the air in the ball, from the cooling of the 
surface, will cause a rise of the fluid in the stem, correspond- 
ing to the volume of air expelled, as shown in the figure. 
The slightest change of temperature will cause this column 
of fluid to move, as the air expands or contracts. We thus 
prove experimentally that solids, fluids, and gases, expand by 
an increase, and contract by a decrease of temperature. 

75. Thermometers. — The law of expansion enables us to 
construct an instrument by which we can measure changes 
of temperature with accuracy. Such an instrument is the 




73. Illustrate the expansion of a solid. 74. Illustrate expansion in a 
fluid ; (a) in water, (b) in a gas. 75. What instrument does the law 
of expansion give us ? 



EXPANSION. 



57 



Thermometer.* Hot and cold are terms of comparison only, 
and teach us nothing of the real difference of temperature 
which bodies may possess. If we place one hand in a vessel 
of iced water, and the other in moderately warm water, we 
at once perceive a strong contrast ; but if we suddenly plunge 
both hands into a third vessel of water at the common tempe- 
rature, our sensations are at once reversed ; the third vessel 
is warm as compared with ice-water, and cold as compared 
with the tepid water. The thermometer, however, enables 
us with the greatest ease to obtain accurate notions of these 
comparative temperatures. 

This valuable instrument was first constructed by Sanc- 
torio, an Italian philosopher, about A. D. 1590. Sanctorio's 
instrument was what is now called an air-thermom- 
eter, because a confined portion of air is employed 
to show the changes of temperature. The annexed 
figure shows the arrangement of the parts. A bulb 
of glass with a long stem is placed with its mouth 
downwards, in a vessel containing a portion of 
colored water. A part of the air is expelled from 
the ball by expansion, (74,) which causes the fluid 
to rise to a convenient point in the stem, to which 
is attached a scale of equal parts, with degrees or 
divisions marked by some arbitrary rule. Thus 
arranged, the instrument indicates with great deli- 
cacy any change of temperature in the surrounding 
air. The portion of air confined in the ball, when 
heated in any degree, expands, and pressing on the column 
of fluid in the stem drives it down, according to the amount 
of expansion or the degree of heat ; and the reverse results 
from a decrease of temperature ; the confined air then con- 
tracting occupies less room, and the fluid rises. The air- 
thermometer is very delicate, but is too limited in its range to 
supply the wants of science ; it has given place to the — 

76. Mercurial, or Common Thermometer, which is now 
in every house. This instrument indicates changes of tem- 




What does this instrument enable us to do ? Illustrate the inaccu- 
racy of our sensations. Who invented the thermometer, and when ? 
Explain his instrument. 76. What instrument is now used in place 
of the air-thermometer ? 



• Named from the Greek thermos, warmth, and metron, measure. 



58 



HEAT. 



perature by the expansion of a fluid in a vacuum. It is form- 
ed of a small glass tube with a very fine bore, (a capillary 
tube, 21,) on one end of which is blown a small ball or bulb 
to contain the mercury, or other fluid with which it is filled. 
This instrument is made by a process which gives us a fine 
illustration of several principles already explained, which we 
will briefly describe. 

It would be impossible to pour any fluid (much less, mer« 
cury) into so small an opening as the fine hair-line of a 
thermometer-bore. If, however, we cautiously hold the ball 
of the tube in the flame of a small alcohol-lamp, the heat, 
expanding the air which it contains, will drive out a portion 
of it at the open end, which is held under the surface of a 
small quantity of mercury, and the air will be seen escaping 
in bubbles through it. Let us hold the tube as nearly hori- 
zontal as possible, and, still keeping its open end under 
the mercury, withdraw the ball from the heat ; as it gradually 
cools, the contraction of the remaining portion of the air 
within the ball, (27,) aided by the pressure of the air on the 
surface of the mercury, (33,) will cause the fluid to rise 
rapidly in the tube, and we shall presently see it fall, drop by 
drop, into the empty ball, until (if the process has been well 
penormed) it is nearly filled. How shall we get rid of the 
remaining air in the ball and tube 1 Let us fit a small funnel 
or cone of paper to the open end of the tube, tie it securely 
there, and put into it a little mercury, which will quite cover 
the open end. Now place the ball in the lamp-flame again, and 
taking care not to heat the stem, cautiously warm the mer- 
cury, until the heavy fluid boils vigorously in the delicate glass 
ball. The air in the tube is driven out by the vapor of the 
boiling mercury, and is seen to escape in bubbles through the 
fluid metal in the paper funnel, which acts as a valve (28) to 
prevent its return. The whole space is now full of the 
invisible vapor of this dense metal, and once more withdraw- 
ing the ball from the heat, the vapor is condensed, and the 
pressure of the air on the surface of the mercury in the 
funnel, instantly forces it into the vacuum beneath, completely 
filling both ball and stem. The operation of thermometer- 
making is now completed by once more warming the ball, to 
expel any remaining portion of the air, and also, if necessary, 



Give the process of making a thermometer. 



EXPANSION. 59 

a part of the mercury in the stem, and at the same instant 
the open end of the tube is sealed by a blow-pipe. On again 
cooling, the mercury contracts, and leaves a vacuum of the 
most perfect description, (33.) We will explain presently 
how the thermometer may be fitted with a scale. 

Alcohol is also employed to fill thermometers which are to 
be used for estimating very low temperatures ; but mercury 
is the fluid preferred for all common cases, because of the 
great uniformity in its rate of expansion. 

In the arctic regions, the temperature, for many weeks 
together, is below the freezing point of mercury, and there alco- 
hol thermometers are indispensable. Pure alcohol has never 
been frozen. 

77. Graduation of Thermometers. — To make the ther- 
mometer of any value as an indicator of temperature, we 
must have a standard of comparison, by which two observers 
with different instruments, and in different parts of the globe, 
may compare the results of their observations. We are 
indebted to Sir Isaac Newton for suggesting the method of 
graduating thermometers. He knew that ice melted, and 
water boiled, always at the same temperatures at the level of 
the sea. By marking the place where the mercury of a 
thermometer stood, in boiling water, and also in a mixture of 
snow or ice with water, two fixed and immutable points are 
obtained, the boiling and freezing of water,* which were found 
by repeated trials, to be at the same relative distance in all 
good instruments. By dividing the space between these 
points into any number of equal parts, the instrument became 
complete, and its indications could be compared with those Of 
any other, graduated on the same plan. 

78. Thermometrical Scales. — In this country and in Eng- 
land, Fahrenheit's scale is chiefly employed. It is unfortu- 
nate that there should be more than one thermometrical scale in 



What is used to fill thermometers to register extreme cold ^f77. 
How is one thermometer compared with another ? What is New- 
ton's mode of graduation ? How is the space between boiling and 
freezing divided ? 



* We shall see hereafter that, although the melting and freezing 
of water take place at the same temperature, under favorable cir- 
cumstances, yet that it is the melting of ice, and not the freezing of 
water, which gives invariably the constant temperature of 32° — the 
freezing point being liable to some variation. 



L 



60 



HEAT. 



aio- = = 





I3i 

m 

ne 
too 
90 
80 
70 

(>0-f 
50 
4ft 
30 
20-£ 
10 



= = *« 



: 90 



use, because it is inconvenient to translate the 
terms of any other nation into our own. The 
scale or division of Celsius (a Swedish phi- 
losopher) is generally used at present in 
continental Europe, and is also called the 
Centigrade scale, because it divides the in- 
terval between the boiling and freezing of 
water into one hundred parts. Formerly the 
French used the graduation of Reaumur, 
which made 80° between boiling and freezing 
water. Fahrenheit (who was a citizen of 
Amsterdam) thought that he had found the 
true zero, or point of greatest possible cold, 
by means of a mixture of snow and salt. 
We now know that there is no such thing as 
an absolute zero* either of heat or cold. 
Fahrenheit divided his scale from his supposed 
zero to the boiling point of water into 212°, 
which places the freezing of water at 32°, and 
leaves 180° between that point and the boil- 
ing of water. Both Celsius (Centigrade) 
and Reaumur made the freezing of water the 
zero of their scales. The degrees of Centi- 
grade are always marked in books C. ; of 
Reaumur R. ; and of Fahrenheit F., or Fahr. 
Thereforeil o C. = o R.=32 o F.; and 100°C= 
80 o R.= 18D°F. ; and keeping these propor- 
tions in mind, it is quite easy to translate the 
reading of one scale into the other. 

The figure annexed shows us at a 
glance the several scales compared. The 
one on the right, marked De Lisle, was 
the contrivance of a French astronomer 



¥ 



Name the principal thermometrical scales ? What number of 
degrees did Celsius make between boiling and freezing water ? 
How many are there in Reaumur's scale ? What was Fahrenheit's 
zero? How many degrees had he above zero to the boiling of 
water ? 



* The word zero is from the Italian, and signifies ' nothing,' and 
was applied to the thermometer in allusion to the supposed absence 
of all heat. 



EXPANSION. 



61 



who proposed to call boiling water zero, and read down- 
wards, by 150°, to the freezing point. It is not used v We 
shall use only Fahrenheit's scale, which is so well understood 
in this country ; and a single example will show how we may 
convert the degrees of Centigrade or Reaumur into those of 
Fahrenheit. 100 o C.=80 o R.=180 o F. is the same as 5C.= 
4R.=9F. Fahrenheit's scale (180°) is to that of Reaumur 
(100°) as 9 is to 5. To reduce Centigrade to Fahrenheit, we 
can multiply by 9 and divide by 5, and add 32° to the quo- 
tient, and vice versa. Suppose we wish to know what 70°C. 
is on Fahrenheit's scale ; we have the proportion 5:9:: 
70° : 126°. If we add 32°, which is the difference between 
zero of F. and C, we have 126° + 32°= 158°, which is the 
number required, for 70°C.= 158°F. In stating thermometrical 
degrees, the sign + is used for points above zero, and — for 
those below. 

79. The Self-Registering Thermometer (often called, also, 
Six's Thermometer) is a form of the instrument contrived for 





Sp 




6 - 


c n 


l,n ii h m 


1 1 1 1 1 n 1 1 1 


i ii i i r i 1 1 . 1 1 1 1 ii 





the purpose of ascertaining the extremes of variations which 
may occur, as, for instance, during the night, or in sounding 
to great depths in the sea, or measuring the temperature of 
an artesian boring. It consists of two horizontal thermome- 
ters attached to one frame, as in the figure ; b is a mercurial 
thermometer, and measures the maximum temperature, by 
pushing forward, with the expansion of the column, a short 
piece of steel wire, of such size as to move easily in the bore 
of the tube ; it is left by the mercury at the remotest point 
reached by the expansion ,* a is a spirit-of-wine thermometer, 
and measures the minimum temperature. It contains a short 
cylinder of porcelain, shown in the figure, which retires with 
the alcohol on the contraction of the column of fluid, but docs 
not advance on its expansion. To use the instrument, it is 

How are the degrees of one scale converted into another ? Give 
examples. 79. Explain Six's thermometer. What registers the 
maximum temperature ? 
6 



L 



62 



HEAT. 



necessary before every observation to incline it, and with a 
slight jar bring the cylinder of porcelain in a to the surface 
of the lluid. 

80. The Differential Thermometer is a form of air-ther- 
mometer, (75,) with two bulbs on one tube, bent twice at right 
angles, and supported as shown in the figure ; a little sulphu- 
ric acid, water, or other fluid, partly fills the stem only, 
(shown by the cross-lines in the figure.) When the bulbs of 
this instrument are heated or cooled alike, no change is seen 

in the position of the column, but the 
instant any inequality of temperature 
exists between them, as from bringing 
the hand near one of them, the column 
of fluid moves rapidly over the scale. A 
modification of this instrument, of great 
delicacy, was contrived by Dr. Howard 
of Baltimore, in which ether was used, 
the bulbs being vacuous of air. It is 
called a differential thermometer, be- 
cause it notes only differences of tem- 
perature, and not actual temperature. 

81. Pyrometers. — All common thermometers are limited 
to comparatively low temperatures. Mercury boils at about 
660°, above which we can judge of temperatures only by the 
expansion of solids. We have thermometers made with 
gases or vapors, and with fluids, and pyrometers made with 
solids. 

A Pyrometer* is an instrument for measuring high tem- 
peratures. The only instrument of this sort which we need 
mention, as it is the only one susceptible of accuracy, is 
DanielPs Register Pyrometer. It consists of a hollow case 
of black lead, or plumbago, into which is dropped a bar of metal, 
(platinum is preferable,) secured to its place by a strap of 
platinum and a wedge of porcelain. The whole is then 
heated, as for instance, by placing it in a pot of molten 




What the minimum ? 80. What is a differential thermometer ? 
Why so called ? 81. What is a pyrometer, and its use ? 



* From the Greek, jner, fire, and metron, measure. A very conve- 
nient form of pyrometer for illustration, is made by all instrument- 
makers, which shows the expansion of a metallic bar, heated by a 
spirit-lamp, moving an index like a clock-pointer. 



EXPANSION. 



63 




been found to be 
highest heat of a 



silver, whose temperature we wish 
to ascertain. The metal bar ex- 
pands much more than the case 
of black lead, and being confined 
from moving in any but an up- 
ward direction, drives forward the 
arm of a lever, as shown in the 
figure, over a graduated arc, on 
which we read the degrees of Fah- 
renheit's scale ; (this graduation 
has been determined beforehand 
with great care.) This instrument 
gives very accurate results; by 
it the melting point of cast iron has 
2786° F., and of silver 1860° F. The 
good wind-furnace, is 3300° F. 

Having, to a sufficient extent, become acquainted with in- 
struments for measuring temperature, and with the principles 
of their construction, we can now proceed intelligently with 
our main subject. • 

82. Expansion of Solids and Liquids. — (1.) Different 
solids expand differently with equal increase of temperature. 
(2.) The same solid expands equally for every equal addition 
of heat below 212°. Between the freezing and boiling of 
water, 350 cubic inches of lead become 351 ; 800 of iron 
become 801 ; and 1000 of glass become 1001. Each solid, 
in fact, has a rate of expansion peculiar to. itself. The same 
is true of liquids. 1000 parts of water between 32° and 
212°, expand to 1046 parts; and 1000 parts of quicksilver 
become 1080 parts. The~expansions are gradual, both in 
solids and liquids, and on withdrawing the heat, they return 
with equal regularity to their former dimensions. Above 
212°, the expansion of both solids and liquids becomes irreg- 
ular and increases. 

83. The unequal expansion of solids is well shown by 
joining firmly, by rivets, two bars, one of iron and one of 
brass, as in the figure. When they are heated, the brass ex- 



What is. the principle of Danieil's pyrometer ? What are some 
of the results obtained by it ? 82. How do solids expand ? How 
with equal increments of heat ? Name 9€*me examples. Also some 
of liquids. Above 212° how do bodies expand ? 83. How is the 
unequal expansion of solids shown ? 



64 



HEAT. 



paneling most, will cause the compound bar to bend, as shown 
(.-•: .. ■ ■ . - '_ i _j_j_j_ -r- -^-a in the lower figure. If 

they are cooled by ice, the 
brass contracting most, 
will bend the united metals 
in an opposite direction. 
84. The Compensation Pendulum gives a beautiful appli- 
cation of the law of unequal expansion to regulating the rate of 
time-pieces. The length of the pendulum 
is altered by variations of temperature, and 
of course the rate of the clock is disturbed. 
A perfect compensation for this error is ob- 
tained by the use of a compound pendulum of 
brass and iron, or other two metals, ar- 
ranged as is shown in figure a, in such a 
manner that the expansion of one metal 
downwards will exactly counteract that of 
the other metal upwards ; thus keeping 
the ball of the pendulum at a uniform dis- 
tance from the point of suspension. The 
shaded bars represent the iron, and the 
light ones, the brass. The same object is 
accomplished by using mercury, as shown 

6 in figure b, contained in a glass or steel 

vessel at the end of the pendulum-rod. 
The expansion which lengthens the rod also 
increases the volume of the mercury; this increase of bulk 
in the mercury raises the centre of gravity to an exactly 
compensating amount, and the clock remains unaltered in 
rate. Watches and chronometers are 
regulated by a like beautiful contrivance. 
The balance-wheel c, on whose uniform 
motion the regularity of the watch or 
chronometer depends, is liable to a 
change of dimensions from heat or cold. 
If made smaller, it will move faster, and 
if larger, slower. To avoid this error, 
the outside of the wheel is made of brass, 
the inside of steel, and cut at two opposite points ; one end of 




84. How is the unequal expansion of metals used in regulating 
time-pieces ? How is the chronometer balance constructed ? 



EXPANSION. 65 

each part is screwed to the arm, and the loose ends of the 
rim, being united by a screw, are drawn in or thrown out 
by the changes of temperature, in precise proportion to the 
amount of change ; thus perfectly adapting the revolution of 
the wheel to the force of the spring. The principle of this 
wheel will be seen in the compound bars. (83.) 

85. Practical applications of the laws of expansion in 
solids are frequently made with great advantage in the arts. 
The rivets which hold together the plates ofiron in steam- 
boilers are put in and secured while red-hot, and on cooling 
draw together the opposite edges of the plates with great 
power. The wheel-wright secures the parts of a carriage- 
wheel by a red-hot tire, or belt of iron, which being quickly 
quenched, before it chars the wood, binds the whole fabric 
together with wonderful firmness. The walls of the Con- 
servatory of Arts in Paris were safely drawn into a vertical 
position after they had bulged badly, by the alternate con- 
traction and expansion of large rods of iron passed across it, 
and so secured by screw-nuts and heated by argand lamps 
as to draw the walls inward. Towers of churches and other 
buildings have been thrown down or otherwise injured by 
the expansion of large iron rods, (anchors,) built into the 
masonry with the design of strengthening them. The me- 
chanical arts are, in fact, full of beautiful applications of the 
principles of expansion. 

86. Unequal Expansion of Water. — The general law of 
expansion for nearly all solids and fluids, especially within the 
limits of the freezing and boiling points of water, is, that each 
solid or fluid expands or contracts an equal amount for every 
like increase and reduction of temperature, each body having 
its own rate of alteration (82.) There are, however, some 
exceptions to this law, of which water offers a remarkable 
example; the comfort, and even habitability of our globe, are 
in a great degree dependent on this exception to the ordinary 
laws of nature. We will briefly explain it, and the effects 
resulting from it. 

If we fill a large thermometer-tube or bulbed glass (like 
the one figured in 74, a) with water, and place it in a cold 



85. Name some other practical applications of the same principle 
in the arts. 86. Explain the unequal expansion of water. 
6* 



66 HEAT. 

situation,* where we can observe the fall of the temperature 
by the thermometer, we shall see the column descend regu- 
larly with the temperature, until it reaches 39 0, 1 F., when 
the contrary effect will take place ; the water then begins 
suddenly to rise in the tube, by a regular expansion, until the 
temperature falls to 32°, when so sudden an expansion takes 
place as to throw the water in a jet from the open orifice, 
and the ball at the same time is not unfrequently broken 
from the solidification of the water. If, on the other hand, 
we heat water in such an apparatus, commencing at 32°, 
we shall find that, until the temperature rises to 40°, the 
fluid, in place of expanding as we might expect, will actually 
contract. Water has, therefore, its greatest density at 39°*1, 
and its density is the same for equal temperatures above and 
below this point; thus we shall find it having a similar 
density at 34° and 45°, and this is true until it reaches the 
point of solidification at 32°. 

87. Beneficial Results. — Let us now observe what useful 
end this curious irregularity in the expansion of water sub- 
serves. When winter approaches, the lakes and rivers, by the 
contact of the cold air, begin to lose their heat on the surface ; 
the colder water, being more dense, falls to the bottom, and 
its place is supplied by warmer water rising from below. A 
system of circulation is thus set in motion, and its tendency, 
if the mass of water is not too large, is to reduce the whole, 
gradually, to the same temperature throughout. When, 
however, the water has cooled to 39°-l, this circulation is 
suddenly stopped by the operation of the law just explained : 
below this point the water no longer contracts by cooling, and 
of course does not sink, but on the contrary expanding, as 
before explained, it becomes relatively lighter, and remains 
on the surface ; the temperature of this layer or upper stratum 
gradually falls, until the freezing point is reached and a film 
of ice is formed. But as ice is a very bad conductor, the 
heat now escapes with extreme slowness ; all currents tending 



At what temperature is it most dense ? How is it at equal tem- 
peratures above and below this point ? 87. Explain the use of the 
irregular expansion of water in its operation in nature. Why does 
not the heat of the water escape after the ice commences forming ? 

* A freezing mixture of salt and ice surrounding it will answer 
the purpose very well. 



COMMUNICATION OF HEAT. 67 

to convey away the cooler parts of the water are arrested, 
and the thickness of the ice can increase only by the slow 
conduction through the film already formed ; the consequence 
is, that our most severe winters fail to make ice of any great 
thickness. Other causes, also, which we shall presently ex- 
plain, co-operate at all times to render the freezing of water a 
very slow process. If this irregularity did not exist, there is 
every reason to believe that the entire waters of the globe* 
would freeze solid : when any portion reached the point of 
congelation, all would become solid at once, like a mass of 
molten metal cooled in a crucible. We cannot fail to be im- 
pressed by the wisdom of that power, which not only frames 
great general laws for the government of matter, but also 
makes exceptions to them, when the welfare of His creatures 
requires them. 

88. The expansion of all gases and vapors is the same 
for an equal degree of heat, and equal increments of heat 
produce equal amounts of expansion. This rate of expan- 
sion is not altered by any change in the compression or elas- 
tic force of the gas, and amounts to xg-^th part of the volume 
of the gas at 0° for each degree of Fahrenheit's scale. 

When gases are near the point of compression at which 
they become liquid, this law becomes irregular. 

The expansion of air by heat, is one cause of winds and 
atmospheric currents. The trade-winds and other regular 
winds so well known to mariners, are the joint result of the 
motion of the earth on its axis, and the rise of heated air 
from the equatorial regions of the globe. 



2. Communication of Heat. — Equilibrium of Temperature. 

89. Equilibrium of Temperature. — A heated body, like 
a red-hot cannon-ball, cools when removed from the source 



What limits the thickness of ice ? What might happen but for 
this ? 88. What is the law of expansion in gases ? What irregularity 
does this law undergo ? What results from the expansion of atmo- 
spheric air ? 89. What is equilibrium of temperature ? Explain 
how a hot body may cool. (1.) (2.) (3.) 

* Sea-water above 32° is not subject to the exception., but it is 
below 28°. 



68 HEAT. 

of heat ; (1) by communicating its heat to the substance 
supporting it, (conduction ;) (2) by the contact of the atmo- 
sphere conveying it away, (convection ;) and (3) by direct 
radiation, or a transmission of rays of heat in all directions 
through the surrounding air, as light (52) is transmitted. 
All these causes act to withdraw the excess of heat from the 
heated body, which thus divides itself equally among surround- 
ing bodies according to their several powers of receiving it, 
until a perfect equilibrium of temperature is produced, the hot 
body has become cool, and the others have gained heat. 

In liquids or gases, this uniform diffusion or distribution of 
temperature takes place rapidly, because of the mobility of 
their particles ; but in solids, much more slowly. Its dif- 
fusion has no connection with the conducting power of the 
fluids, however, which are among the worst of conductors. 

90. Conduction of Heat. — Each solid has its own pecu- 
liar power of conducting heat, but in all it is a progressive 
operation, the heat seeming to travel from particle to particle 
with greater ' or less rapidity, according to the conducting 
power of the solid. If we hold a pipe-stem or glass rod in 
the flame of a spirit-lamp or candle, we can heat it to red- 
ness within an inch of our fingers with no inconvenience ; 
but a wire of silver or copper would burn us in a very short 
time when at the distance of many inches from the flame. 

This is owing to a 
o ° c s ° ° T^ difference inherent in 

© these solids, which we 
call conducting power. - The progress of conducted heat in 
a solid is easily shown, as in the annexed figure, representing 
a rod of copper, to which are stuck by wax several marbles 
at equal distances ; one end is held over a lamp, and the 
marbles drop off, one by one, as the heat melts the wax ; 
that nearest the lamp falling first, and so on. If the rod is 
of copper, they all drop very soon ; but if a rod 
of lead or platinum is used, the heat is conveyed 

(1 , much more slowly. Little cones of various 

i i m lii ■ • a 

metals, and other substances, may be tipped 



How does the diffusion of heat take place in gases and liquids ? 
How in solids ? 90. Explain conduction in solids. What experi- 
ments are named in illustration of it ? 




COMMUNICATION OF HEAT. 69 

with wax or bits of phosphorus,* as shown in the figure b, 
and placed on a hot surface. The wax will melt, or the phos- 
phorus inflame, at different times, according to the conduct- 
ing power of the various solids. *>^ccurate experiments have 
been made, which have enabled uPtoiarrange most solids in 
a table showing their conducting pliers. The metals as 
a class are good conductors, while wo<WL charcoal, fire-clay, 
and similar bodies, are bad ones. Tn%^gold is the best 
conductor, and may be represented by the nuW ro gr 1000 ; then 
marble will be 23-5, porcelain 12, and fire-cla^lJ.. Metals 
compared with each other are very different in conducting 
power. Thus — 



Gold, 


1000. 


Iron, 


375. 


Silver, 


973. 


Zinc, 


363. 


Copper, 


898. 


Tin, 


304. 


Platinum, 


381. 


Lead, 


180, 



91. The sense of touch gives us a good idea of the dif 
ferent conducting power of various solids. All the articles 
in an apartment have nearly the same temperature ; but if 
we lay our hand on a wooden table, the sensation is very 
different from that we feel on touching the marble mantel or 
the metal door-knob. The carpet will give us still a different 
sensation. The marble feels cold, because it rapidly conducts 
away the heat from the hand ; while the carpet, being a very 
bad conductor, retains and accumulates the heat, and thus 
feels warm. Clothing is not itself warm, but being a bad 
conductor retains the heat of the body. A film of confined 
air is one of the worst conductors ; loose clothes are therefore 
warmer than those which fit closely. For the same reason, 
porous bodies, like charcoal, are bad conductors ; and a 
wooden handle enables us to manage hot bodies with ease. 

92. The conducting power of fluids is very small. This 
is contrary to the general impression of people, who think, 
from the ease with which a tea-kettle boils, that liquids con- 



How are the different classes of bodies as conductors ? Name 
some examples. Give some examples from the table. 91. Explain 
the relation of our sense of touch to the conducting power of bodies. 



* If phosphorus is used, some screen must be employed to cut off 
the radiant heat, which will otherwise inflame it prematurely. 



70 



HEAT. 



duct heat with facility. A simple and instructive experiment 
will prove to us that the conducting 
.of fluids is very low. A glass, 
lat in the figure, is filled nearly to 
'brim with water. A thermometer- 
)e, with a large ball, is so arranged 
"m it that the ball is just covered, and no 
more, with the water; the stem passes out 
at the bottom through a tight cork, and 
has a little colored fluid, L, in it, which 
will of course move with any change of 
bulk in the air contained in the ball. 

Thus arranged, a pointer, I, marks 
exactly the position of one of the drops 
of inclosed fluid, and a little ether is 
poured on the surface of the water, and 
set on fire. The flame is intensely hot, 
and rests on the surface of the water ; 
the column of fluid at I is, however, 
unmoved, which would not be the case 
if any sensible quantity of heat had 
been imparted to the water. The 
warmth of the hand touching the ball 
will at once move the fluid at I, by ex- 
panding the air within. By heating a 
vessel of water on the top, then, we 
should never succeed in creating any- 
thing more than a superficial boiling ; 
at the depth of a few inches the water would remain cold. 

93. The conducting power of gases is also very small. 
Heat travels with extreme slowness through a confined por- 
tion of air (91.) This is a very different thing from the 
convection of heat in gases, which we will presently explain. 
Double windows and doors, and furring so called, of plas- 
tered walls, afford excellent illustrations of the slow conduction 
of heat through confined air. We have no proof that heat 
can be conducted in any degree by gases and vapors. To 
illustrate the relative conducting power of solids, fluids, and 
gases; if we touch a rod of metal heated to 120°, we shall 




92. How is the conducting power of fluids ? Give an experiment- 
al illustration. 93. How is it in gases ? Give illustrations. 
What comparative trial in solids, fluids, and gas, is named ? 



COMMUNICATION OF HEAT. 



71 



be severely burned; water at 150° will not scald us if we 
keep the hand still, and the heat is gradually raised ; while 
air at 300° has been often endured without injury. The 
oven-girls of Germany, clad in thick socks of woolen, to pro- 
tect the feet, enter ovens without inconvenience where all 
kinds of culinary operations are going on, at a temperature 
above 300° ; although the touch of any metallic article while 
there would severely burn them. ^ 

94. Convection of Heat. — Fluids and gases are heated 
by what is termed Convection. Heat applied from beneath 
to a vessel containing water, heats 
the layer or film of particles in 
contact with the vessel. These ex- 
pand with the heat, and consequent- 
ly, becoming lighter, rise, and colder 
particles supply their place, which 
also rise in turn, and so the whole 
contents of the vessel come succes- 
sively into contact with the source of 
heat, and convey it away. This is I 
well illustrated in the annexed figure, 
which shows how water acts in a 
vessel of glass, when heated at a 
point beneath by a spirit-lamp. Each 
particle in turn comes under the 
influence" of heat, because of the per- 
fect mobility of the fluid, and the heat 
is thus conveyed to, and distributed 
throughout, the whole mass. A 
series of such currents exist in every 
vessel in which water is boiled, and they are rendered more 
evident, by throwing into it a few grains of some solid, (like 
amber,) so nearly of the same gravity of water, that it will 
rise and fall with the currents. A perpetual circulation is 
thus established in fluids, which serves to keep up the equi- 
librium of temperature in our globe. 

95. In the air, and in all gases and vapors, the same thing 
happens. The earth is heated by the sun's rays, and the 




What is said of the oven-girls in Germany ? 94. How are fluids 
and gases heated ? Explain what is meant by convection of heat. 
Give an account of the experiment. 



72 HEAT. 

film of air resting on the heated surface rises, or tends to 
rise, to be replaced by colder air. The rarified air may be 
easily seen on a hot day, rising from the surface of the earth, 
being made visible by its different refractive power. Hence 
arise many aerial currents and winds. The currents of the 
ocean are also influenced by the same cause. 

96. Convection and conduction of heat will, therefore, be 
carefully distinguished from each other by the learner. Heat 
is, so to speak, transported rapidly in fluids by convection, 
while by conduction it travels slowly and progressively from 
particle to particle, within the limits of the body subject to it. 

97. Radiant Heat. — We have spoken of the sun's rays 
as composed of both light and heat ; these rays of heat 
proceed from all hot bodies, at all temperatures, for the 
slightest disturbance of the equilibrium of temperature will 
occasion their emission. Radiant heat is subject in all respects 
to the same laws, and possesses the same habitudes as light. 
It can pass through many substances ; it is subject to reflec- 
tion, absorption, refraction, and polarization. Radiation of 
heat takes place in a vacuum much more rapidly than in air, 
and is, therefore, quite independent of any conducting me- 
dium. 

98. Refection of heat is shown by the concave parabolic 
mirror. All rays of heat or light falling on this form of me- 
tallic mirror are collected atF, the focus, and 
a hot body placed in the focus will have its 
rays sent forth in parallel straight lines, as 
shown in the figure. A second and simi- 
lar mirror may be so placed as to receive 
and collect in a focus all the rays proceed- 
ing from any body in the focus of the other, 
where they will become evident by their 
effect on the thermometer. If the hot 
body be a red-hot cannon-ball, and the mir- 
rors are carefully adjusted, so as to be ex- 
actly opposite each other in the same line, the accumulation 
of heat in the focus of the second mirror is such, as to inflame 
'dry tinder, or gunpowder, even at twenty feet distance. This 

95. Explain the origin of aerial and oceanic currents. 96. Con- 
trast the effects of convection and conduction. 97. What is radiant 
heat ? From what bodies does it flow, and why ? What is said 
of its properties ? 98. Explain the reflection of heat, and the me- 
tallic mirrors. 






COMMUNICATION OF HEAT. 73 

arrangement is shown in the annexed figure, and the experi- 
ment is a most strik- 
ing and satisfactory 
one. It is quite es- 
sential that the mir- 
rors should be highly- 
polished ; otherwise 
the heat, in place of 
being reflected to the 
second mirror, will be absorbed by the dull surface. A 
bright mirror will not become sensibly hotter from the near 
approach of the hot body, nearly the whole heat being re- 
flected; but a black mirror will grow rapidly hot, and will 
then emit heat itself, by what has been called secondary 
radiation. 

99. The formation of dew is owing to radiation, cooling 
the surface of the earth so rapidly, that the moisture of the 
air, which is always abundant in summer, is condensed upon 
it, as we see it on the outside of a tumbler of iced-water in a 
hot day. Radiation takes place more rapidly from the sur- 
face of grass and vegetation, than from dry stones or dusty 
roads : for this reason, plants receive abundant dew, while the 
barren sand has none. 

100. Radiation of cold was formerly supposed to occur, 
because a mass of ice placed in the focus of one mirror, 
caused the thermometer in the other to fall. The true expla- 
nation of this is, that the thermometer, in this case, is the hot 
body, and parts with heat to melt the ice, and thus restore the 
equilibrium of temperature. Cold is merely the absence of 
heat, and is a negative, and not a positive quality. 

101. Absorption of Heat. — All black and dull surfaces 
absorb heat very rapidly when exposed to its action, and part 
with it again by secondary radiation. The sun shining on a 
person dressed in black, is felt with much more power than 
if he were dressed in white. The former color rapidly ab- 
sorbs heat, while from the latter a considerable part of it is 
reflected. The color of bodies has nothing to do with their 
radiating powers, and one colored cloth is as warm in winter 
as another, as regards the emission of heat. 



What experiment is shown by the mirrors ? What if they are 
dull or black ? 99. Explain dew. 100. Explain the supposed ra- 
diation of cold. 101. How does color affect absorption ? 

7 



74 HEAT. 

102. The nature of the surface of bodies has the greatest 
effect on their several powers of radiation. Hot water in a 
bright tin canister, or a polished silver tea-pot, will remain 
hot very much longer than in a vessel with dull or roughened 
surfaces. A coating of lamp-black on the surface of a tin 
canister, placed in the focus of the mirror, will radiate five 
times more heat from boiling water than clean lead, and 
eight times more than bright tin, as proved by the differential 
thermometer. Bright metals have the lowest radiating power, 
and hence are selected to preserve heat in those substances 
which we wish to keep hot. For the same reason, they are 
the worst vessels in which to heat a fluid. The effort to boil 
water in a bright copper tea-kettle, is very tedious ; as soon, 
however, as the surface becomes sooty from the fire, the heat 
passes in rapidly. The nature and not the color of the sur- 
face affects radiation. A dull cast-iron stove radiates more 
heat than a polished sheet-iron one — the openness of the 
pores and great number of points of the cast-iron materially 
aid its radiating power. 

3. Transmission of Heat through Bodies. 

103. The rays of heat from the sun, like the rays of light 
from the same luminary, pass through transparent substances 
with little change or loss. Radiant heat, however, from ter- 
restial sources, whether luminous or not, is in a great mea- 
sure arrested by many transparent substances. If the sun's 
rays be concentrated by a metallic mirror, the heat accom- 
panying them is so intense at the focus as to fuse copper and 
silver with ease. A pane of colorless window-glass inter- 
posed between the mirror and the focus, will not stop any 
considerable part of the heat. If the same mirror is presented 
to any other source of heat, however, (as the red-hot ball, 
98,) the glass plate will stop nearly all the heat, although the 
light is undiminished. We thus distinguish two sorts of 
calorific rays, which are sometimes called Solar and Culina- 
ry Heat, and we discover that substances transparent to light 



Does it affect radiation ? 102. What chiefly affects radiating pow- 
er ? Give illustrations. 103. Give the distinction between rays of 
heat from the sun, and those from most terrestrial substances. How 
are the latter affected by glass and other transparent substances ? 



TRANSMISSION OP HEAT THROUGH BODIES. 75 

are not, so to speak, transparent to heat in a like degree. 
This property is distinguished from transparency by the term 
Diathermancy* Bodies allowing the passage of the heat 
are said to be diathermous, while those allowing the passage 
of light are said to be diaphanous. f Bodies which complete- 
ly arrest the passage of radiant heat are said to be adiather- 
mous. 

Bodies which are highly transparent or diaphanous, are 
often completely adiathermous, so that the transparency of a 
body is not connected with its diathermancy. 

Thus glass of various sorts arrests from 47 per cent, to 
67 per cent, of the rays of heat, while common alum in per- 
fectly clear masses allows the passage of only 9 rays in 
100." On the other hand, rock-salt stops only 8 rays in 100, 
92 passing freely through. These facts are easily shown, 
when no other means are at hand, by placing a tablet of 
rock-salt and one of glass in a situation to be exposed to the 
heat of a fire. The glass will soon grow so hot#s to burn 
the fingers, from the quantity of heat arrested by it, while 
the salt will hardly be affected. A large air-thermometer, or 
a delicate differential one, with one ball blackened, will also 
answer to make many of these changes of temperature 
evident, in the absence of the more delicate means explained 
in the next section. 

104. Melloni's Apparatus. — Nearly all the knowledge we 
possess on this interesting branch of science, we owe to the 
labors of a distinguished Italian philosopher, M. Melloni, who 
has invented a most beautiful apparatus, by which all these 
observations and discoveries have been made. Its general 
arrangement is represented in the annexed figure. The 
degree of heat is measured in this instrument, not by a ther- 
mometer, (which would be altogether too rude an indicator 
of such minute changes of temperature as are here shown,) 



What is Diathermancy ? What is meant by diaphanous ? What 
by adiathermous ? Are these properties united generally ? Give 
instauces. 



* From the Greek, dia, through, and thermos, heat, in allusion to 
the passage of heat through substances. 

f From the Greek, dia, through, and phaino, to shine. 



76 HEAT. 




but by what is called a ther mo-multiplier, or multiplier of 
heat. This is an arrangement of little bars of the two metals, 
antimony and bismuth, about fifty of which are soldered 
together by their alternate ends, the whole being with its 
case not more than 2^ inches long, by J to ^ of an inch in 
diameter. The least difference of heat between the opposite 
ends of this little battery will produce an electrical current 
capable of influencing a magnetic needle, in an instrument 
called a galvanometer. The needle of the galvanometer will 
move in exact accordance to the intensity of the heat. This 
is so delicate an instrument, that the radiant heat of the hand 
held near the battery will cause the needle to move some 10° 
over its graduated circle. In the figure, a is the source of 
heat, (an oil-lamp in this case,) b a screen having a hole to 
admit the passage of a bundle of rays ; c is the substance on 
which the heat is to fall ; d the ther mo- multiplier, or battery, 
which is to receive the rays after they have passed through 
the substance c. Two wires connect the opposite members 
of this battery with the galvanometer 6, which, for steadiness, 
is placed on a bracket attached to the wall. Thus arranged, 
and with various delicate aids which we cannot now explain, 
a vast number of most instructive experiments have been 
made on radiant heat from different sources, and its effect 
ascertained on various substances. Four different sources of ( 
heat were employed : (1) the naked flame of an oil-lamp ; (2) 
a coil of platinum wire heated to redness by an alcohol-lamp ; 
(3) a surface of blackened copper heated to 734°, and (4,) 
the same heated to 212° by boiling water. The first two 
of these are luminous sources of heat, the last two not so. 



104. Explain Melloni's apparatus from the figure. What sources 
of heat were used ? 



TRANSMISSION OF HEAT THROUGH BODIES. 



77 



The following table will show a few of the principal re- 
sults. 



Names of interposed substances, common 
thickness, 0-102. 



Rock-salt, transparent and colorless, 

Iceland-spar, 

Plate -glass, 

Rock-crystal, 

Rock-crystal, brown, 

Alum, transparent, 

Sugar-candy, 

Ice, pure and transparent, . . . 



Transmission of 100 


rays of heat from 










0, 


~ S 


m 


OS 


B 
S 


- - 


S* 2 


a 
%& 


o 


«'& 


o 


o 


92 


92 


92 


92 


36 


28 


6 





39 


24 


6 





38 


28 


6 





37 


28 


6 





9 


2 








8 











6 












Thus it appears that rock-salt is the only substance which 
permits an equal amount of heat from all sources to pass. 
In other cases the number of rays passing seem proportioned 
to the intensity of the source. M. Melloni has called rock- 
salt the glass of heat, as it permits heat to pass with the same 
ease that glass does light. It is supposed that the difference 
found by experiment in the diathermancy of bodies, is owing 
to a peculiar relation which the various rays of heat sustain 
to these bodies, exactly analogous to that difference in the 
rays of light which we call color. Thus all other bodies, 
except salt, act on heat as colored glasses act on light, 
entirely absorbing some of the colors, and allowing others to 
pass. Thus rock-salt may be said to be colorless as respects 
heat, while alum and ice are in the same sense almost black. 
Opake bodies, like wood and metals, entirely prevent the 
transmission of heat ; but dark-colored crystal is seen, by 
the table, to differ only 1 from white crystal, and even per- 
fectly black glass does not entirely stop all heat. 

105. By cutting rock-salt into prisms and lenses, the heat 
from radiant bodies may be reflected, refracted, and concen- 
trated, like light, and doubly refracting minerals, like Iceland- 
spar, will polarize it. All these interesting results, however, 
\re must pass without further notice. 

Give some illustrations of the results from the table. What has 
rock-salt been called, and why ? To what are the different powers 
of bodies in this respect supposed to be owing ? 105. What other 
attributes of light have been discovered in radiant heat, and how ? 

7* 



78 HEAT. 

4. Specific Heat. — Capacity of Bodies for Heat. 

106. Specific heat is that amount of heat required to 
raise any body through a given number of degrees of tem- 
perature, as, e. g., 10°. It is a remarkable fact, and one of 
great importance, that the same quantity of heat cannot raise 
different bodies through an equal number of degrees of tem- 
perature. If equal measures (say a pint) of mercury and 
water be exposed to the same source of heat, we shall find 
that the mercury will attain its highest temperature about 
twice as soon as the water ; and on removal from the fire, it 
will cool in half the time. If a pint measure of water at 
150° be mixed quickly with an equal measure of the same 
fluid at 50°, the two measures of fluid will have the tempera- 
ture of 100°, or the arithmetical mean of the two tempera- 
tures before mixture. If, however, we take one measure of 
water at 150°, and an equal measure of mercury at 50°, and 
rapidly mix them, we shall find that they will have the 
temperature of 118°. The mercury has gained 68°, and the 
water lost only 32°, or about half as much. Hence we infer 
that the same quantity of heat can raise the temperature of 
mercury through twice as many degrees as that of water. 
We thus prove, by actual trial, that each body (solid, fluid, 
or gas) has its own relation to the amount of heat required 
to raise it a given number of degrees of heat, and this amount 
being peculiar to each body, is called its specific heat. As 
water is adopted as the standard of comparison for specific 
heats, the specific heat of mercury will be to water as 32 to 
68, or nearly 0*47. It is more convenient to compare bodies 
by weight than by measure ; and hence if we divide the 
specific heat by measure (0-47) by the specific gravity of 
mercury, (13*5,) we obtain the number, 0-035, its specific 
heat, by a comparison of weights. The process just de- 
scribed for determining specific heat, is called the method of 
mixtures. 

1 07. The method of mixtures can be used to obtain the 
specific heat of solids as well as fluids. Thus a bar of cop- 
per of a pound weight may be heated to a temperature of 
400°, and then put into a pound of water at 50°; when the 



106. What is specific heat ? Illustrate this in the case of mercury 
and water. Give the specific heat of mercury by measure and 
weight. What is this method called ? 



CHANGES PRODUCED BY HEAT. 



79 



equilibrium is restored, both will have the temperature of 72°. 
The copper has lost 328°, and the water has gained 22°. 
The specific heats being then as 228 : 22, that of the copper 
is found to be ■££% =0*095. Other methods have been used 
to determine specific heats, but it is foreign to our present 
purpose to describe them. The following table will show the 
specific heats of a number of substances : 



Water, 


1-000 


Copper, 


0-095 


Ether, 


0-520 


Lead, 


0-031 


Alcohol, 


0-660 


Gold, 


0-032 


Sulphuric 


Acid 0-333 


Antimony, 


0-051 


Mercury, 


0-033 


Tin, 


0-056 


Silver, 


0-057 


Phosphorus, 


0-118 


• Zinc, 


0-095 


Glass, 


0-197 


Iron, 


0-114 


Lime, 


0-205 



The specific heat is found to be most intimately connected 
with the chemical character of the substance, and many curi- 
ous and important inferences have been made from the study 
of these relations. We shall have occasion to refer to this 
subject again, in the chapter on Chemical Philosophy. 

5. Changes produced by Heat in the state of Bodies. 

108. Uzquef action. — The change of a solid to a fluid is 
called liquefaction, and is always attended by a remarkable 
absorption of heat. Water is a substance familiarly known 
under all three states of solid, fluid, and gaseous ; and the 
melting of ice will furnish us a good instance of the pheno- 
mena which take place in the process of liquefaction. We 
have already seen that two equal measures of water at diffe- 
rent temperatures have, when mingled, a temperature which 
is the mean of their previous temperatures, (106.) If, how- 
ever, we take a pound of ice (solid water) at 32°, and a 
pound of water at 212°, we shall find, when the ice is melted, 
ftir^Pfhe two pounds of water have the temperature of only 
52° ; the ice gains only 20°, while the water has lost 160°. 
There are, then, 140° of heat lost in producing this change. 
We can take another mode of trial. Let us expose a pound 



107. Is it used for solids, and how ? Give some examples from 
table. 108. What is liquefaction ? Explain and illustrate the change 
of ice to water. 



80 HEAT. 

of ice at 32°, and another pound of water at the same tempe- 
rature, to a constant source of heat, in two vessels every way 
alike, and note the changes of temperature by the thermome- 
ter. When the ice is all melted, we shall find that the water 
into which it is converted has still only the temperature of 32°, 
while the other pound of water has risen from 32° to 172° ; 
here again we see the loss of 140° of heat used in converting 
the ice into water. We may reverse the last experiment, 
and lake equal weights of ice at 32° and water at 172°, and 
mix them ; the ice will soon be all melted, and the mixture 
will have the temperature of only 32° : so that, in whatever 
way we may make the trial, we constantly observe the loss 
of 140° of heat. This is called the heat of fluidity, it being 
necessary to the existence of the water in a fluid state, and it 
is also designated latent heat, because it is lost, absorbed, or 
concealed, as it were, and no indication of it can be found by 
the thermometer. 

109. Congelation. — If a vessel filled with water at 52° 
be placed in an atmosphere of 32°, it will rapidly cool down 
to 32° by the loss of 20° of temperature. After this, it will, 
as may be seen by the thermometer, remain at 32°, until it is 
all converted to solid ice; although we cannot doubt that 
it is all the while giving out a quantity of heat, which had 
before been insensible or latent. If the water had been ten 
minutes in cooling from 52° to 32°, (or in losing 20°,) then 
it would require one hour and ten minutes, or seven times as 
long, for it to become completely frozen. If, then, in equal 
times it lost equal degrees of heat, its latent heat will be 20° 
X 7 = 140°, which is the same result as before. 

Thus it is by a wise order of Providence that the freezing 
and thawing of snow and ice are extremely slow and grad- 
ual processes. If water became solid at once on reaching 
32°, the water would be suddenly frozen to a great depth ; 
and if ice melted as quickly on reaching the same 'terapeia-/ 
ture, the most sudden and dreadful floods would ac&lh^rj 
these events, and the common changes of the seasons >vWirf[ 
be calamitous to human comfort and life. 



What amount of heat is in all these cases unaccounted for ? What 
is this lost heat called ? What becomes of it ? 109. State the phe- 
nomena observed in freezing. How do we then discover the same 
quantity of latent heat in water ? What reflection is hence drawn 
in the order of Providence ? 



LIQUEFACTION. 81 

110. Freezing is a warming process. — Water may be 
cooled below its freezing point and still remain liquid, if its 
surface be covered with a thin film of oil, and if it is in a thin 
smooth vessel, kept quite still ; but the least disturbance will 
cause it, when in this situation, to become solid at once, and 
the temperature will immediately rise from 23° or 24° to 32°. 
The freezing of a part has therefore given out heat enough to 
raise the 7 temperature of the whole from 24° to 32°, of through 
8°. In like manner, it is true that melting is a cooling pro- 
cess, although it seems paradoxical to say so. A solid can 
melt ^become liquid) only by absorbing heat from surround- 
ing bjbdies, which must, of course, become cooler. Hence 
in part the cooling influence of an iceberg, which is often felt 
for many leagues, or of a large body of snow on a distant 
mountain. 

111. Freezing mixtures, or the means used to produce 
artificial cold, owe their powers to the principles just ex- 
plained. Ice-cream is frozen by a mixture of snow or 
pounded ice with common salt. In this case the two solids 
are rapidly changed to fluids ; the ice is melted by the 
salt, and the salt is dissolved by the water from the melting 
ice. Both these operations absorb (or render latent) a large 
quantity of heat. The surrounding bodies are called on to 
supply the heat required, and the cream, in a thin metallic 
vessel, loses heat so rapidly from this cause, as to be soon 
turned to ice. The thermometer will fall in this operation 
to 0° F. ; and this was the very experiment by which 
Fahrenheit (78) assumed that he had attained to a true zero 
of cold. 

Nitrate of ammonia dissolved in water at 46° will sink 
the temperature to zero, and the exterior of the vessel be- 
comes at once thickly covered with hoar-frost. Common 
saltpetre, (nitrate of potassa,) dissolved in water, lowers its 
temperature several degrees, and is therefore much used in 
the hot regions of Asia, where it abounds, for cooling wine. 
Mercury may be frozen by using a mixture of three parts of 
chloride of calcium, and two of dry snow ; this mixture will 
sink the temperature from +32° to —50°. It should be di- 
vided into two pretty abundant portions ; the first of which 



110. How is freezing a warming process ? Illustrate this. Why 
is melting a cooling process? 111. What are freezing mixtures? 
To what do they owe their power ? Give some examples. 



82 



HEAT. 



serves to cool down the mercury, and the second is used 
when the first is exhausted, and completes the work. 

But all other means of producing cold are insignificant, 
when compared to the power of solidified carbonic acid gas, 
in a vacuum, by means of which, Dr. Faraday has succeeded 
in obtaining a temperature of — 175° below zero of Fahren- 
heit's thermometer. 

112. The melting point of every substance is very uni- 
form, and each body has its own, which is often one of its 
most characteristic marks. Thus it is the melting of ice, 
and not the freezing of water, that gives the constant tempera- 
ture of 32°. By no contrivance can we raise the tempera- 
ture of ice above 32° ; nor can any other solid be heated a'bove 
its melting point and remain a solid. Some substances, in 
melting, pass at once, like ice, to a state of perfect fluidity ; 
others have an intermediate pasty state. The following table 
contains the melting points of a few bodies at both ends of 
the scale : 



Mercury, — 39 c 


Zinc, 773° 


Potassium, -\- 136 


Silver, 1873 


Newton's Alloy, 2*2 


Gold, 2016 


Tin, 442 


Cast Iron, 2786 


Lead, 612 


Platina, (above) 3280 



113. Diminution of volume in a body will cause a por- 
tion of the latent heat to become sensible. Thus, numerous 
blows will condense iron or gold, and so much heat will be 
evolved, that blacksmiths in this way sometimes kindle their 
fires. Water poured on quicklime combines with it, with 
the escape of much heat ; the water in this case taking on 
the solid form. Sulphuric acid and water, when mingled, 
give out great heat, and the bulk of the mixture is less than 
that of the two before mixing. Liquefaction is always a 
cooling process, and solidification a heating one, to all sur- 
rounding bodies. A certain quantity of heat may be consi- 
dered as necessary to preserve each body in its natural con- 
dition : if it be condensed, less is required, and it gives out 



What is the greatest cold thus produced ? 112. What is said of 
the melting points ? Name some examples of extremes from the 
table. 113. How does diminution of volume affect the latent heat, 
of bodies ? Name some examples. 



VAPORIZATION. 83 

the excess ; and if expanded, it absorbs more. Dr. Black, 
of Scotland, was the first who made known to us the beau- 
tiful philosophy of latent heat, and the phenomena of lique 
faction and vaporizatipn. 

114. Difference between heat and temperature. — It is 
easy to see, from what has been said, that the thermometer 
cannot tell us any thing of the amount of heat in a body, since 
the latent heat is quite insensible to any thermometrical test. 
We speak more properly, then, when we say that we know 
the temperature of a bodv, than to say we know its heat. 

6. Vaporization. — The boiling points of Bodies. 

115. A continuance of the heat which melted the ice (108) 
into water, will turn the water into vapor or steam. The 
phenomena which attend this physical change are not less 
curious or instructive than the last. 

If we place a known quantity of water over a steady source 
of heat, we shall see the thermometer indicating each mo- 
ment a higher temperature, until, at 212°, the fluid boils ; 
after which, the thermometer indicates no further change, 
but remains steadily at the same point until all the water is 
boiled away. Let us suppose that, at the commencement 
of the experiment, the temperature of the water was 62°, and 
that it boiled in six minutes after it was first exposed to the 
heat : then the quantity of heat which entered into it each 
minute was 25°, because 212°, the boiling point, less 62°, 
leaves 150° of heat accumulated in six minutes, or 25° each 
minute. Now if the source of heat continue uniform, we 
shall find that in forty minutes all the water will be boiled 
away ; and hence there must have flowed into the water, to 
convert it into steam, 25° X 40=1000°. One thousand 
degrees of heat, therefore, have been absorbed in the process, 
and this constitutes the latent heat of steam. What we have 
already said on the latent heat of liquids will render this more 
clear. So much heat was imparted to the water, that if it 
had been a fixed solid, it would have been heated to red- 
ness ; and yet the steam from it, and the fluid itself, had 
during the whole time only a temperature of 212°. 

Who first made known these laws? 114. Distinguish between 
heat and temperature. 115. What takes place when we heat water ? 
Explain the process and the amount of heat absorbed by boiling 
water ? What do you call this heat ? 



84, 



HEAT. 



116. The large amount of latent heat contained by steam, 
becomes again sensible on its condensation to water. This 
enables us to make great use of steam as a means of con- 
veying heat. The steam takes up a large quantity of heat, 
and transports it to the point where we wish it applied. One 
gallon of water converted into steam, at the ordinary pressure 
of the atmosphere, will raise five gallons and a half of ice- 
cold water to the boiling point. In this way we can boil 
water in wooden tanks, heat large buildings by steam-pipes, 
and make numberless other useful applications of steam-heat 
in the arts. 

117. The distillation of water (or any other fluid) affords 
a good illustration of the quantity of latent heat conveyed 
away in the vapor. In the arrangement here figured, a glass 
retort (R) is made to contain a quantity of water, which is 
boiled by a lamp below, the steam is conveyed by the bent 

neck to a receiving- vessel, 
in which it is condensed, 
being surrounded by cold 
water or ice poured into 
the dish placed to support 
it. After the water boils 
in the retort, its tempera- 
ture does not rise any 
further, but the vapor con- 
veys the heat of the lamp 
over to the condenser. The 
water which surrounds it 
will grow rapidly hot from 
the latent heat of the steam, 
rendered sensible by its 
reconversion into water. 
For this reason the condensing water must be frequently 
changed. In metallic stills, the condenser is a long metallic 
tube, bent into a spiral, (called a worm,) and surrounded by 
cold water. 

118. The latent heat of steam, which may be set down at 
about 1000°, (although it is stated more accurately at 967°,) 




116. How does the latent heat of steam again become sensible ? 
How much ice-cold water will one gallon turned to steam boil ? 
117. How does the process of distillation illustrate this ? 118. How 
does the latent heat of steam compare with that of the vapor of 
other fluids ? 






VAPORIZATION. 



85 



is greater than that of any other known fluid. The latent 
iieat of fluids has no connection with their boiling point ; since 
many liquids which boil at high temperatures have little 
latent heat, and the reverse. The annexed table shows the 
boiling points and latent heat of the vapor of several common 
liquids. 



Liquids. 


Boiling Point. 


Latent Heat of Vapor. 


Water, 


212° 


967° 


Alcohol, 


172 


442 


Ether, 


96 


302 


Petroleum, 


320 


178 


Oil of Turpentine, 


314 


178 


Nitric Acid, (strong,) 


248 


532 


Ammonia,* (liquid,) 


140 


837 



119. Boiling or Ebullition takes place in a liquid when 
it becomes so hot that its vapor can rise in bubbles to the sur- 
face, and escape uncondensed by the atmospheric pressure, 
or the temperature of the fluid. The elasticity (or tension) 
of the vapor then becomes greater than the united pressure of 
the fluid and the air. When the boiling is vigorous, a great 
number of these bubbles of uncondensed vapor rise to the 
surface at the same instant, and the liquid is thrown into 
violent agitation. If a vessel containing cold water be heated 
suddenly, the lower surface receives the most heat ; bubbles 
of vapor are formed, and rise a little way, when, meeting the 
colder water, the vapor is at once condensed, and the liquid, 
before sustained by the elastic vapor, falls with a sudden jar 
on the bottom of the vessel, producing a series of little ex- 
plosions. This may be well seen in a glass flask suddenly 
heated by a lamp. When the heat is gradually applied, it is 
so evenly and quietly distributed that this effect is not per- 
ceived. 

The boiling point is much affected by the nature of the 
vessel. In a metallic vessel, water boils at 210° and 211°. 
If a glass vessel be coated inside with shellac, water boils in 
it at 211°; but if it be thoroughly cleaned with sulphuric 



Is latent heat connected with the boiling point ? Illustrate this 
from the table. 119. What is boiling ? Illustrate this. How does 
the nature of the vessel affect it ? 



Specific Gravity, 0*945. 



86 HEAT. 

acid, it may be heated to 221° or more, without the escape 
of bubbles. A few grains of sand, or a little fragment of 
wire, or a small piece of charcoal, will, however, at once 
equalize these differences, and cause the water to boil quietly 
at 212°. This simple means will prevent the unpl^isant jar 
from sudden escape of vapor, and frequent fracture of the 
glass vessel. 

120. The pressure of the atmosphere determines the boil- 
ing point of fluids ; and when we speak of the boiling point, 
we always mean ebullition under the ordinary pressure of the 
air, or 30 inches of the barometer, (33.) It follows, there- 
fore, that by a diminution of pressure, water may be made 
to boil at a much lower temperature than 212°. In ascend- 
ing high mountains, the boiling point falls with the elevation, 
from the diminished pressurefcf the air. On this account, a 
difficulty is experienced at the -Hospital of Saint Bernard, on 
the Swiss Alps, in cooking eggs and other viands in boiling 
water. This place is 8400 feet above the sea, and water 
boils there at 196° ; on the summit of Mount Blanc, it boils 
at 187°. We see that it is the temperature, and not the boil- 
ing which performs the cooking. The Rev. Dr. Wollaston 
contrived an instrument to determine tke height of mountains 
by the boiling point. He found an ascent of 5^0 feet to be 
equal to a decrease of 1° in the boiling point ; and with a 
thermometer having large spaces, accurately subdivided, T oVo 
of a degree may be read. 

121. Boiling under Diminished Pressure. — An experi- 
ment easily performed, gives a very good illustration of the 
phenomena of boiling under diminished pressure. A small 
quantity of water is boiled in a glass retort, or in a bolt-head, 
like that in the following figure ; when the water has boiled 
a short time, a good cork, previously well fitted to the orifice, 
is firmly inserted, and the vessel removed from the heat. It 
may now be supported in an inverted position, with the mouth 
under water, as seen in the annexed figure. The boiling 
will still continue, and more rapidly than before ; and if we 
attempt to check it by cold water poured on the ball, we shall 
only cause it to boil more vehemently. A little hot water 



120. What influences the boiling point ? Mention the boiling point 
of water on Mount Blanc, and the elevation necessary to produce 1° 
of difference in the boiling point. 121. Explain the experiment of 
ooiling under diminished pressure. 



VAPORIZATION. 



87 



will, however, at once arrest the ebullition of the confined 
fluid. In this case, the air is driven out of the vessel on 
the first boiling of the water, and as we close the orifice, 
while the steam is still issuing, there is only the vapor of 
water in the cavity. As this condenses from 
cooling, the pressure on the water diminishes, 
and it boils more easily from the heat it still 
contains ; the affusion of cold water, by pro- 
ducing a more perfect condensation, occasions 
a more violent ebullition. The hot water, 
however, increases the elasticity of the uncon- 
densed vapor, and represses the boiling. These 
alterations can be produced as long as the 
water in the vessel is warmer than the cold 
water poured on it. When cold, the space 
over the water will be a good vacuum, and 
if we turn the water from the ball into the 
neck, it will fall like lead, with a smart blow 
and rattling sound. This is sometimes called 
the water-hammer. The perfection of the 
vacuum can be tested by withdrawing the cork 
under water ; the pressure of the atmosphere 
will then drive in a quantity of water, equal to the vacuum 
produced by the first expulsion of the air. 

122. Freezing and Boiling in a vacuum. — A little ether 
under an air-jar on the plate of the air-pump will flash into 
vapor as soon as the pressure is removed by working the 
pump ; and water may be frozen 
by its own evaporation, over a good 
air-pump, arranged as in the figure. 
The water is contained in a watch- 
glass on a tripod, over a shallow 
dish of sulphuric acid, and the whole is covered by a low 
air-jar. On working the pump, the water evaporates so 
rapidly in the vacuum as to boil even at 72°, its vapor is 
instantly absorbed by the sulphuric acid, and in this way 
both the sensible and latent heat are removed so rapidly, that 
the water is frozen solid while still apparently boiling. 

123. The Cryophorus, or frost-bearer\ offers another 





What principles are here brought into view ? How is the absence 
of the air made evident ? 122. How is water frozen in a vacuum ? 




88 HEAT. 

illustration of the same facts. This little instrument, invented 

by Dr. Wol- 
laston, is only 
a bulb of glass, 
containing a lit- 
tle water, and 

connected by a long bent tube with another bulb or protube- 
rance, which is emiy^te space over the water is a vacuum, 
the tube having been sSBr when the water was boiling. On 
placing the empty stenTfrifca freezing mixture of ice and salt, 
the vapor of the water is- so rapidly condensed as to freeze 
the fluid in the ball which is remote from the freezing mixture. 

124. Practical application of these facts is made in the 
arts on a large scale, in manufacturing sugar. The boiling 
of the syrup is performed in vacuo, in large pans of copper, 
holding several hundred gallons, the air and vapor being 
removed from the vessels by a steam-engine ; the syrup is 
thus rapidly boiled down at a temperature of 150° to 180°, 
without any danger of burning. Vegetable extracts are 
frequently made, and saline solutions boiled, in the same 
way. Nothing in the arts shows more clearly the value and 
beauty of scientific principles. 

125. Elevation of the Boiling Point by Pressure. — If 
water is boiled in a vessel, which can be closed after the 
escape of the atmospheric air, as in the brass boiler (a) of 
the annexed figure, we can easily submit it to any desired 
degree of pressure, and thus elevate the boiling point. This 
boiler is provided with a thermometer (c) whose ball is 
within the steam cavity ; and also with a barometer tube, 
(&,) which descends into some mercury, placed in the bot- 
tom. It is supported by a tripod (f) over a lamp, (e,) and a 
stop-cock (d) cuts off the external air. As soon as the 
water in it boils, the steam accumulates, and, pressing on 
the mercury, forces it up the tube, against 'the imprisoned 
air. The relation of air to pressure has already been 
explained, (30.) When the mercury indicates 30 inches, ot 
double the pressure of the air, the thermometer will indicate a 
temperature of 250°*5. In this way the boiling point of water has 



123. What is the cryophorus ? Explain the principle of its action. 
124. What practical application is made of these facts ? 125. How 
does pressure affect the boiling point ? Explain the apparatus here 
figured. 



VAPORIZATION. 



been raised to 429°-34,or nearly to the 
melting point of tin; the pressure 
was then 375 pounds to the inch, 
or 25 atmospheres. Mr. Jacob 
Perkins heated steam so highly, 
that a jet of it set fire to combusti- 
ble bodies. 

126. The elastic power of steam 
:n contact with water is limited 
only by the strength of the contain- 
ing vessel : if steam be heated with- 
out water, {not in contact with it,) 
then its elastic or expansive power 
is exactly like that of other gases or 
vapors, (88.) 

127. The increase of volume in 
changing from a liquid to a gaseous 
state is such, that 1 cubic foot of water 
becomes 1700 cubic feet of steam ; 
or a cubic inch of water becomes 
nearly a cubic foot of steam ; while 
1 cubic foot of alcohol and ether 
yield, respectively 493 and 212 cubic 
feet of vapor. 

Water is, therefore, incomparably 
the best fluid from which to generate 
steam for a moving power ; for its 
higher boiling point is more than 
made up by the greater volume 
of its vapor, and the cost of ■ 
fuel is in proportion to the la- 
tent heat of equal volumes of vapor. 

to ether for this purpose, in the proportion of 2500 to 1000. 
The latent heat of steam diminishes as the heat rises, so 
that the heating power of steam at 400° is no greater than 
that of an equal volume at 212°. These facts are of the 
greatest value in the arts. 




Thus water is superior 



What is the boiling point of water under 30 inches of mercury ? 
How high has it been raised ? 126. How does elevation of tem- 
perature affect steam ? 127. What is the increase of volume from 
vaporization of water? Of alcohol ? Of ether ? 

8* 



90 



HEAT. 



I 



128. The Steam- Engine. — The principle of this appa. 
ratus is simple, and easily illustrated by the simple instrument 

a here figured, which 

was contrived by 

Dr. Wollaston. A 

glass tube (a), with a 

bulb to hold a little 
• z^n* water, is fitted with 

a piston. A hole 

passes from the 

under side through 

the rod, and is 

closed by a screw 

at a. This screw 

is loosened to ad- 
mit the escape of 
the air, and the water is boiled 
over a lamp ; as soon as the steam 
issues freely from the open end 
of the rod, the screw is tighten- 
ed, and the pressure of the steam 
then raises the piston to the top 
of the tube; the experimenter 
withdraws it from the lamp, the 
steam is condensed, and the air pressing freely on the top of 
the piston forces it down again ; when the operation may be 
repeated by again bringing it over the lamp. 

In the common condensing engine, a cylinder (a) is fitted 
with a solid piston, the rod of which moves through a tight 
packing in the cover, and to it the machinery is attached. A 
pipe (d) brings the steam from a boiler to the valve arrange- 
ment, (c,) by which the steam is admitted, alternately, to 
the top and bottom of the cylinder ; and also an alternate 
communication is opened with the condenser, (b.) Thus, 
when the steam enters at the top, (in the direction of the ar- 
row,) that at the bottom of the piston is driven through the 
lower opening to (b) where it is condensed. The valves are 
moved at the proper time by the machinery. 

129. Evaporation from the surface of liquids takes place 




128. Explain the principles of the steam-engine from Dr. Wollas- 
ton's instrument. Explain the general structure of the condensing 
engine from the figure. 



VAPORIZATION. 91 

at all temperatures, while ebullition, it will De remembered, 
occurs only at a particular temperature for each fluid. Even 
snow and ice waste by evaporation, at temperatures too low 
to melt them. Mercury rises in vapor, even at the temper- 
ature of 60° ; for Dr. Faraday found at that temperature that a 
slip of gold-leaf suspended in a close vessel %vas whitened 
by amalgamation with the vapor of the mercury* 
The state of the atmosphere as to dryness and 
pressure influences natural evaporation, which is 
greatly increased by heat and a rapid wind. It 
must be remembered that all the water which falls 
to the earth in snow and rain has arisen in evapo- 
ration. That natural evaporation takes place 
only from the surface is proved by its being en- 
tirely prevented by a film of oil on the surface of 
the fluid. 

130. Influence of Pressure on Evaporation. — 
If we introduce a few drops of water into the va- 
cuum above the mercury in a barometer tube (33), 
the level of the mercury will be reduced by the 
vaporization of a part of the water. The tension 
of the vapor is increased, by a rise of temperature : 
we may slip a larger tube over the barometer 
.tube, the lower end of which dips under the mer- 
cury, and then fill the intervening space with hot 
water. The vapor of the confined water will 
force down the column of mercury in direct pro- 
portion to the temperature ; and by means of a 
thermometer and a scale of inches we can tell 
exactly the tension of the vapor of water for every 
temperature under 212°. 

131. Maximum Density of Vapors. — If we 
nearly fill with mercury three barometer tubes closed at one 
end, and into the open end of one pour a little ether, into the 
second some alcohol, and into the third some water, and then 
invert them with their mouths beneath mercury, we shall see, 
on withdrawing the finger from the open end, that the 



129. What is the difference between evaporation and ebullition ? 
130. How does pressure affect evaporation ? How is the tension of 
vapor measured ? 




92 



HEAT. 




mercury will be depressed least by the 
water, more by the alcohol, and most of 
all by the ether, (about 10 inches at 60°.) 
The addition of more of each fluid will have 
no effect in lowering the mercury, the tem- 
perature remaining the same. There is, 
therefore, a point of density of the vapor 
which cannot be passed without again con- 
verting it to a liquid. This is easily shown 
by inclining the tube containing the ether 
out of a vertical position ; the more nearly 
horizontal it becomes, the less ether can re- 
main in vapor, because the increased pressure 
forces it into a fluid state. The same fact is 
beautifully shown in the annexed figure, where 
the barometer-tube with ether is depressed in a 
deep cistern of mercury. The film of liquid 
ether on the surface of the mercury in the 
tube is seen to increase as the tube descends, 
until the ethereal vapor is all reconverted to a 
fluid ; on diminishing the pressure of the 
finger, the liquid ether again flashes into vapor. 
The weight of 100 cubic inches of aqueous 
vapor at 212° in the greatest state of density 
ever obtained, is 14*962 grains; while the 
same at 32° is only *136 grains. The point 
of maximum density of a vapor is lowered by 
cold as well as by pressure, and when these 
two effects are united, we can convert many 
gases, which are quite permanent at the com- 
mon pressure and temperature of the air, into liquids, and 
even to solids. 

132. Diffusion of Gases and Vapors. — The vapor of 
water will rise and fill a confined vessel of air, and have the 
same tension as if no air were present, h will take a longer 
time to do it, but as much will ultimately rise as if the space 
were a vacuum. The air seems to be an impediment only 
to the rapid rise of the vapor. On the same principle, prob- 
ably, is explained the curious and important fact, that, when 
different gases are in contact, they will not remam separate, 



131. What is the maximum density of vapors * 
from the figure. 



F< **s-.*e th'« 



VAPORIZATION. 93 

but will soon mingle uniformly, even against the force of 
gravity. Our atmosphere, for instance, is composed of two 
gases, the specific gravities of which are as 976 to 1130, 
and we might suppose that the heavier would be at ^ 
the bottom, as would be the case in two such liquids 
as water and oil. But they are found to be in a state 
of uniform mixture. If we connect together by a tube 
two bottles containing, one a light gas, hydrogen, and 
the other a heavier gas, oxygen, and place the light 
one uppermost, in a few hours we shall find them per- 
fectly commingled ; as may be proved by the fact, that 
the mixture will explode violently on touching a match 
to the open mouth of one of the vessels, which we £3 
know a mixture of these two gases will always do. F \y 
The same effect will take place through a very fine | 
tube, or even through a plug of plaster-of-paris, or 
through a membrane, as of gold-beater's skin. The 
degree of condensation of the air or vapor hasjio effect 
in the operation of the law of the uniform diffusion of gases. 
133. Dew-Point. — Watery vapor is never absent from the 
air; but its quantity is very variable, depending on the causes 
already named, (129.) When the air is highly charged with 
humidity, it deposits dew on any substance colder than itself. 
A glass of iced water in summer is immediately covered with 
a coat of condensed vapor from the surrounding air. When 
a warm humid morning succeeds a cool night, we see the 
pavements and walls of the houses reeking with deposited 
water, as if they had been drenched with rain. If we drop 
bits of ice into a tumbler of water having the same temper- 
ature with the air, and watch the fall of a thermometer 
placed in it, we can note with accuracy the temperature of 
the water, when it has cooled so far that dew begins to be 
deposited on the clean surface of the glass. This tempera- 
ture is called the dew-point ; and the number of degrees be- 
tween the temperature of the air, and of water cooled to that 
degree at which dew begins or ceases to be deposited, is an accu- 
rate indication of the actual dryness of the air. The nearer the 
dew-point is to the temperature of the air, the more moisture 
does it contain, and vice-versa. In this climate, in summer, 
this difference amounts often to 40° or more, and in India it 

132. Menti:n the facts relating to the diffusion of vapors and 
gases. Illustrate this. 133. What is the dew-point ? How does 
it indicate the dryness or humidity of the climate ? 



94 



HEAT. 



has been known to be as much as 61° ; that is, with an ex^ 
ternal temperature of 90°, the dew-point has been seen as low 
as 29°. The amount of moisture in the air has a great 
influence on the indications of the barometer, and it is always 
requisite, in making barometrical observations, to make a 
correction for the tension of the vapor of water in the air. 

134. Hygrometers* are instruments to determine the 
amount of moisture in the air. One much used is called 
the wet bulb hygrometer, and consists of two sim- 
ilar delicate mercurial thermometers, the bulb 
of one of which is covered with muslin, and is 
kept constantly wet by wa- 
ter, led on to it by a string 
from a tube in the centre. 
The evaporation of the water 
from the wet bulb reduces the 
temperature of that thermome- 
ter to which it is attached, in 
proportion to the dryness of 
the air, and consequent rapidi- 
ty of evaporation. The other 
thermometer indicates the ac- 
tual temperature, and the dif- 
ference being noted, a mathematical formula en- 
ables us to determine the dew-point. 

But the most delicate and beautiful instrument 
for this use is that of Mr. Daniell, which is constructed on 
the principle of the cryophorus, (123.) It is represented 
in the annexed figure, (a.) The long limb ends in a bulb 
which is made of black glass, that the condensed vapor 
may be more easily seen on it. It contains a portion 
of ether, into which dips the ball of a small and delicate 
thermometer contained in the cavity of the tube. The whole 
instrument contains only the vapor of ether, air having been 
removed. The short limb carries an empty bulb, which is 
covered with muslin. On the support is another thermome- 
ter, by which we can observe the temperature of the air. 
When an observation is to be made by this instrument, a 
little ether is poured on the muslin : this evaporates rapidly, 

134. What are Hygrometers ? Describe the wet bulb. Describe 
the Hygrometer of Prof. Daniell. 




* From the Greek hugros, moist, and metron, measure. 



VAPORIZATION. 95 

and of course reduces the temperature of the other ball, 
(122.) As soon as this has fallen to the dew-point, the 
moisture collects and is easily seen on the black glass. At 
this instant, the temperature indicated by the thermometers is 
noted down, and the difference gives us the true dew-point. 

135. The Spheroidal state of bodies, as it is called, is a 
curious and instructive instance of the low conducting power 
of vapors. When water or any other liquid is projected in 
drops on a surface, heated considerably above its boiling 
point, it will assume a spheroidal form, roll about with activity, 
and evaporate with extreme slowness. Water assumes this 
condition at 298° ; and a grain and a half of water in this 
state at 392° requires 3-30 minutes to evaporate : at a dull 
red heat, the same quantity will last 1*13 minutes, and at a 
bright red, 0-50, the rate of evaporation increasing with the 
temperature. The water, in these experiments, does not 
touch or wet the hot surface, but is kept at a sensible dis- 
tance from it by the elastic force of an atmosphere of its own 
vapor. This vapor is a non-conductor, and its formation 
abstracts the sensible heat from the fluid ; so that, notwith- 
standing the proximity of the red-hot metal, the temperature 
of the fluid is found to be always lower than its boiling point, 
being, for water, 206°, for alcohol, 168°, and for ether, 91°. 
A modification of this process enables us to perform the 
surprising experiment of freezing water in a white-hot crucible, 
by the aid of liquid sulphurous acid in the spheroidal state. 

136. Liquefaction and Solidification of Gases. — We 
have said that, by the united aid of cold and pressure, many 
gases have been made fluid, and even solid. No degree of 
mere pressure, not even 50 atmospheres, (or 750 lbs. to the 
square inch,) can alone produce this result. By combining 
the two agents, Dr. Faraday has succeeded in reducing fifteen 
aeriform bodies to the liquid or solid state. The simple appa- 
ratus required for many of these results, is only a small tube 

of glass, bent as in the 
figure, at an'obtuse angle, 
in which are placed the 
materials for generating 
the gas ; for instance, 

135. What is meant by the spheroidal state ? How does it illus- 
trate these principles? Explain the experiments mentioned in this 
paragraph. Is the temperature of the fluid in this state as high as 
its boiling point ? 136. How are gases made fluid or solid ? 




96 HEAT. 

powdered bicarbonate of soda and water in one end, and sul- 
phuric acid in the other, to generate carbonic acid gas ; they 
are separately introduced, and the tube then sealed by the 
blow-pipe. On reversing the position of the tube, the acid 
can be made to run down on the carbonate of soda, and 
the carbonic acid gas will be set free, but cannot escape 
from the tube. The empty end is then placed in a freezing 
mixture, and the gas is condensed into a liquid by its own 
pressure. Some hazard attends these experiments, and 
the operator should be protected by gloves and a mask 
of wire-gauze ; for the tubes occasionally burst under the 
enormous pressure, and might wound him severely. Car- 
bonic acid treated in this way becomes a clear transparent 
crystalline solid, at temperatures below — 71°, at which point 
it melts into a perfect limpid fluid, which is not so heavy as 
the solid. M. Cagniard de la Tour has shown, that at a 
certain temperature and pressure, a liquid becomes a clear 
transparent vapor, or gas, having the same bulk as the liquid. 
At this temperature, or one a little greater, no additional 
pressure, however great, would convert the gas into a liquid. 
Dr. Faraday thinks that this state comes on with carbonic 
acid at about 90°, and with a pressure above 50 atmospheres. 
137. Liquefaction and Solidification of Carbonic Acid. 
— M. Thilorier has contrived an apparatus for condensing 
carbonic acid on a large scale. The arrangement is shown 
in the accompanying figure ; g is the generator of the gas, a 
strong cast-iron vessel, hung by centres on a frame, (f;) in 
it is put the requisite quantity of carbonate of soda and water 
and a tube (a) of copper, holding an equivalent amount ot 
strong sulphuric acid ; the cap is strongly screwed in, and 
the position of the apparatus inverted, by turning it over in 
the frame ; the acid then runs out among the carbonate of 
soda, and an enormous pressure is generated by the succes- 
sive portions . of gas evolved ; after a time, when no more 
gas is produced, the generator is connected by a metallic tube 
with the receiver, (r ;) stop-cocks of peculiar construction 
are fixed on the top of both vessels, and being opened, the 
liquefied gas collects in r, which is cooled by a freezing mix- 
ture for the purpose of condensing it. In this way, several 
charges of the condensed carbonic acid gas are accumulated 



Explain the process. What has M. Cagniard de la Tour shown ? 
137. Describe M. Thilorier's apparatus for condensing carbonic acid. 



ELECTRICITY. 



97 




in r. It can then be drawn off 
by a jet (j) secured to the top, 
which enters a metallic box, (&,) 
having perforated wooden han- 
dles. The rapid evaporation of 
the condensed gas here absorbs 
so much heat from the rest, that 
a considerable portion is convert- 
ed to a fine white solid, like dry 
snow. The author has repeat- 
edly formed balls of this snow of 
considerable size. When thus 
made solid, it wastes away very 
slowly, and may be handled 
and moulded with ease. If suffered to rest on the hand, 
however, it destroys the vitality of the flesh, like a hot iron. 
It is now in a condition analogous to bodies in the spheroidal 
state, (135;) being surrounded by an atmosphere of its own 
vapor, the radiation of heat to it from surrounding bodies is 
cut off, and it acquires the very low temperature of — 146°. 
If it is wet with ether in a capsule containing mercury, the 
latter is frozen solid, and can then be hammered with a wooden 
mallet, and drawn out like lead. If it is moistened with ether 
in vacuo, with certain precautions, the greatest degree of 
cold yet observed is produced; viz: 174° below zero of 
Fahrenheit. The greatest cold before known was — 148°, 
and the greatest natural cold ever recorded by man was 
— 60°, which was found by Captain Ross in his polar 
voyages. 

We now see how entirely the gaseous, liquid, and solid 
states of bodies are dependent on heat and pressure. It 
is more than probable that all the bodies now known to us 
as permanent gases may be reduced to the fluid or solid 
state, by means similar to those which have already been 
used. 

IV. ELECTRICITY. 



138. There is a remarkable power inherent in all things, 
which we call electricity,* and which, so far as we know, 

What temperature has been reached by aid of this condensed 
gas ? How is the lowest artificial temperature found ? What do 
we now see from these facts ? 



* From the Greek, electron, amber, the substance in which this 
9 



98 ELECTRICITY. 

is inseparable from matter. It has been classed with light 
and heat, as an imponderable agent, and is doubtless very 
closely related to, if not identical with these forces, the three 
being, perhaps, only modifications of one and the same 
power. It is so intimately connected with matter, as to be 
evolved, in some form or degree, with every change, either 
mechanical or chemical, which matter undergoes. As was 
said of heat, (69,) we know it only by its effects, as manifested 
on or through matter. We shall consider this power under 
its most remarkable forms of existence or manifestation, 
regarding them all, however, as modifications of one and the 
same thing. These are (1,) the Electricity of Magnetism ; 
(2,) that of Friction, or Statical Electricity ; (3,) that of 
Chemical Action, Galvanism, or Voltaism, called also, 
Dynamical Electricity ; and (4,) Thermo-electricity, or 
Electricity from Heat. 

1. Magnetic Electricity, or Magnetism. 

139. Lode-stone* — A kind of iron-ore has been known 
from remote antiquity which has the property of at- 
tracting to itself small particles of iron, and which is called 
the lode-stone. By contact, it can impart its virtues to iron 
and steel, and also in a slight degree to cobalt and nickel. 
As it abounded in Magnesia, (a province of ancient Lydia,) 
it was called by Pliny, magnes, and hence the name magnet. 
A bar or needle of steel, which has received the magnetic 
„ influence, when suspended on a point, as in the 

figure, will be found to have a directive tend- 
ency, by which one end turns invariably to the 
north. The terms, -f- and — , (plus and minus,) 
are also used to indicate the. north and south 
poles. The needle is, therefore, said to 
have polarity, and the end turning north is 
commonly called the north pole, and the other end the south 

138. What is said of electricity ? How is it classed ? How 
divided, (1 ?) (2?) (3 ?) (4 ?) 139. What is the lode-stone ? 

power was first noticed by the ancients, more than 600 years B. O 
Modern philosophers have given the name of the substance to the 
unknown power. 

* Sometimes spelt improperly load-stone. It is from the Saxon, 
laden, to lead or direct. 




MAGNETIC ELECTRICITY. 99 

pole. If we bring the north end of a magnetic bar near 
to the similar end of the suspended needle, fe ^..w^ii^ 
the latter will move away, as indicated by the 
arrows, being repelled by the similar power of the bar. If, 
however, we bring the end N, towards the opposite end of 
the needle S, it will be attracted to the bar, and strive to 
move as near to it as possible. The reverse is, of course, 
true of the opposite end of the bar. If, in place of a mag- 
netic bar, we had used a bar of unmagnetic iron, we should 
have found both ends of the suspended needle equally, but 
less powerfully, attracted by it. We thus learn, (1,) that the 
magnet has polarity, and (2) that poles of the same name re- 
pel, and those of opposite names attract each other. This 
is the simple and important law of magnetic action. 

(=1 140. Induction of Magnetism. — The 

manner in which a magnet, or lode-stone, 
imparts its own power to surrounding 
substances, is called induction, and 
[those bodies capable of manifesting this 
power are said to be magnetized 
3 ^V by the inductive influence. Thus, 

^N^ a series of bars of iron laid about 
^ a magnetic bar, as in the figure, 
• will all become magnetic by in- 

duction, while they are under the influence of the 
magnet; and in obedience to the law just stated above, 
their ends next the N are all S, and their remote ends/ 
all N. Every magnet is surrounded by an atmosphere 
of influence, which has its centre in the poles of the 
magnet, and diminishes as the square of the dis- 
tance, being in this respect like the law of gravi- 
tation. This decrease of force is prettily illustrated 
by an experiment shown in the annexed cut. The bar 
magnet holds a large key; this can hold a second 
smaller than itself; this, a nail ; the nail, a tack-nail ; 
and lastly, a few iron-filings are held by the tack-nail, 
and the whole receive their magnetism by induction 
from the bar, and each article has its own separate 
polarity: an n and s.(or + and — ) pole being opposed to 

Explain its action. Can its virtues be imparted, and to what ? 
What do we know of the suspended needle, (1 ?) (2 ?) 140. What 
is induction of magnetism ? Illustrate this ?^How is the power 
as regards distance ? Give an experimental illustration. 

L.cfC. 



100 ELECTRICITY. 

each other at every junction. This effect will take place 
through a glass-plate, or a small interval of air. 

141. Permanent Magnets. — These can be made only of 
hardened steel. Soft iron and steel are magnets only while 
under the power or influence of other magnets, and lose 
their own power as soon as removed from them. Mag- 
netism is imparted by ' touch? as it is technically called, from 
a previously existing magnet. An unmagnetic bar of hardened 
steel, when properly rubbed by the poles of a magnet, will 
itself soon acquire polarity and magnetic power. Every 
magnet is considered as made up of a great number of 
small magnets, so to speak, each particle of steel having 
polarity, and attracting and repelling every other. We 
cannot conceive of one sort of polarity existing without the 

n s 71 s n s nsnsnsnsns other. Thus, in the figure, 

N aSliXEX^SES^SI^SbfSs we see a magnified repre- 
c*i="a»a5a53aS3 sentation of this condition. 
Each little magnet has its own n and s. Those which occupy 
the middle of the bar, being acted on alike in all directions, 
can show no power ; but the force accumulates toward each 
end, until we find the greatest power in the last range of 
particles, which we term the poles. 

If we dip a magnetic bar in iron-filings, we shall find only 
the ends attracting a tuft of the metallic particles, while the 
middle is free. If two magnetic bars, however, like the 
figure, are placed together, (+ and — ,) and a sheet of 
paper laid over them, they will attract iron filings scattered 

on the paper, in the way 
represented in the figure ; 
here a pair of central poles 
have power to attract the 
iron, which the middle 
part of the simple bar had not. The particles of iron 
arrange themselves in what are called magnetic curves. If 
the paper is jarred, this effect is rendered more striking. 

142. Artificial Magnets are made of all forms, the 
most common being the so called horse-shoe magnet, 

U shaped like the annexed figure. It is found that the 
power of magnets is much increased by uniting 

141. How are permanent magnets made ? How is the power sup- 
posed to be distributed ? Why have the poles more power than the 
centre ? If two bars are laid together, how is it ? 142. What 
forms are given to artificial magnets ? 




MAGNETIC ELECTRICITY. 101 

several thin plates of hardened steel, each of which is sepa- 
rately magnetized. A bar of soft iron, called the keeper, is 
placed across the poles of a u magnet, to prevent it from 
losing power; and if it be made to hold a weight nearly 
equal to its power, it will be found to gain strength daily, and 
in like manner to lose its magnetism if unemployed. 

143. The Earth's Magnetism. — The earth is a great 
magnet, and the magnetism which we see in bars of steel 
ana the lode-stone, is the result of induction (139) from the 
earth. The magnetic poles of the earth are not in the same 
points with the poles of revolution or the axis of the earth, and 
for this reason the magnetic needle does not point to the true 
north and south, but varies from it more or less, and differs 
at different times, as the magnetic pole alters its position. 
This is called the variation of the needle, and amounts, at 
New Haven, to 6° 10' W., (in 1840,) and at Philadelphia 
to 3° 52' W., (in 1837.) As unlike poles attract each other, 
the end of the needle pointing north is, in fact, its south pole, 
viewing the earth as a magnet. 

The magnetism of the earth is beauti- 
fully shown by the dipping needle^ repre- 
sented in the annexed figure. The needle 
(n) is suspended on the horizontal bar, (a,) 
so as to move in a vertical plane, instead 
of horizontally, as in the compass-needle. 
The graduated vertical circle (c) is placed in 
the magnetic meridian, and the needle then 
assumes, in this latitude,* the position shown in the figure, 
dipping down at an angle of 73° 26'-7. Over the magnetic 
equator it would stand horizontal, being equally attracted in 
both directions. At either magnetic pole it would be ver- 
tical. 

The horizontal variation of the needle, its dip, and the 
intensity of the polar attraction, are subject to daily and local 
changes, from the fluctuation in the amount or direction of 
this force ; and daily and even hourly observations have now 

143. What is said of the earth's magnetism ? How is it shown ? 
Is the magnetic pole coincident with the pole of revolution ? What 
is dip, and what variation ? Are they constant ? 

* Lat. 41° 18\ Ion. 17° 58', in September, 1839. 




102 ELECTRICITY. 

for several years been made in all parts of the world, to 
determine with accuracy the limit of these variations, and the 
laws which govern them. 

144. Magnetism from the earth is induced in all bars of 
steel or iron, which stand long in a vertical position. Tongs 
and blacksmiths' tools are often found to be magnetized. A 
bar of iron held in the magnetic meridian, and at the proper 
dip, becomes immediately magnetic from the induction of the 
earth ; and the effect may be hastened by striking it on the 
end with a hammer ; the vibration seems to aid in inducing 
the magnetic force. The tools used in boring and cutting 
iron are generally found to be magnets. 

1 45. Magnetics and Diamagnetics. — Dr. Faraday, in 1 845, 
made the important discovery that all solid and fluid sub- 
stances were subject to the influence of a powerful magnet, 
but in a manner different from that in which iron and nickel 
are influenced by the magnetic force. We shall presently see 
(166) that a bar of iron suspended on a pivot will take a 
place at right angles to the direction of the magnetic or gal- 
vanic current, or will come to rest in the equator of magnetic 
force. Now a bar of bismuth, or a stick of phosphorus, 
under the same circumstances, will act in a manner precisely 
the reverse of the iron, and will come to rest in the magnetic 
or polar plane. All bodies, which under the magnetic power 
act like iron, are called magnetics, while those which re- 
semble bismuth in their behavior under the same circum- 
stances, are called diamagnetics. A few bodies of each class 
are enumerated in the following list, where we observe that 
iron and bismuth are at the extremes, each standing as the 
type of its own class, while air and vacuum occupy the zero, 
or neutral point of quiescent inactivity. Iron, nickel, cobalt, 
manganese, palladium, crown-glass, platinum, osmium, — 0° 
air and vacuum, arsenic, ether, alcohol, gold, water, mer- 
cury, flint-glass, tin, heavy-glass, antimony, phosphorus, 
bismuth. It is a curious sight to see a piece of wood, or of 

144. How are bars of iron and steel affected by the earth's mag- 
netism ? 145. What was Faraday's discovery in 1845 ? Into what 
two classes are bodies divided in reference to their behavior under 
magnetic influence ? Of which is iron the type ? Of which is bis- 
muth ? How are the classes contrasted ? Enumerate a few of 
each class. Is this action confined to metals ? Mention some 
singular examples. 



ELECTRICITY OF FRICTION. 



103 



beef, or an apple, or a bottle of* water, repelled by a magnet ; 
or taking the leaf of a tree and hanging it up between the 
poles, to observe it take an equatorial position. 

2. Electricity of Friction; or Statical Electricity. 

146. Electricity is evolved by several of the same causes 
which we have already (69) named as sources of heat. 
Friction excites it abundantly ; chemical action still more so. 
It attends animal life, and is powerfully exhibited in some 
animals, as in the torpedo, and electrical eel : heat evolves it, 
and we have reason to believe that the sun's rays are per- 
petually exciting electrical currents in the earth. Like heat, 
it neither adds to or subtracts from the weight of matter ; 
but unlike heat, it produces no change in dimensions, and 
does not affect the power of cohesion in bodies. In powerful 
discharges, however, it overcomes cohesion by rending or 
fusion. All matter is subject to its influence, and it can be 
transferred from an excited body to one previously in a neu- 
tral state. 

147. Electrical Excitement. — If we briskly 
rub a glass tube with warm and dry silk, and 
bring it near to any light substance, as a feather 
suspended by a thread, a flock of cotton, some / 
shreds of silk, or, as in the figure, to two balls .-( 
of pith, suspended on a hook by delicate wire, w 
the light substances will at first be strongly attracted to the 
tube, but in an instant will fly off 
again, as if repelled by some unseen 
force, and any further effort to attract 
them to the excited glass will only 
cause their further removal. Each 
separate thread of silk and each 
pith-ball seems to retreat as far as 
possible from the glass tube and from 
the other threads. An artificial head 
of hair or shreds of dry paper shows 
this in a striking manner, when 
placed on the conductor of an excited 
electrical machine. Each hair stands 

146. How is electricity evolved ? Contrast it with heat. 
147. Explain the first facts in electrical excitement. How are the 
pith-balls and head of hair affected i 




104 



ELECTRICITY. 



aloof from every other, as if instinct with hatred. If now, 
in the place of the glass tube, we use a stick of sealing-wax, 
rubbed with dry flannel, and present this to the pith-ball 
which has been excited by the glass tube, we shall find a 
very strong attraction manifested between them ; the light 
substance previously excited by the glass, will move to the ex- 
cited resin much more actively than a substance not previously 
excited in this way ; and two substances separately excited, 
one by the glass and the other by the resin, will attract each 
other with equal power. One of these is called vitreous, and 
the other resinous electricity. These simple phenomena form 
the basis of all electrical science. 

148. Electrical Polarity. — We see in the facts just stated 
a strong resemblance between the two sorts of electrical ex- 
citement and the opposite powers of the magnet. The vitreous 
is to the resinous electricity as the north pole of a magnet is 
to the south. Hence we call the vitreous the positive elec- 
tricity, and the resinous the negative electricity. Each par- 
ticle of matter thus 
influenced by electrical 
excitement must have 
polarity, like the mag- 
netic needle, attracting 

'*" and repelling, accord- 
ing as it is acted on by like or unlike forces. Thus a row 
of pith-balls, as in the figure, will all become excited by 
induction, or influence, and the signs plus and minus will 
explain how they stand related to each other. Magnetism, 
as it is usually understood, is confined to two or three metals ; 
while electricity can, with proper precautions, be excited in 
all substances. 

We cannot conceive of one sort of electrical excitement 
existing without the other ; thus the glass tube is -f- , but the 
silk which rubs it is — , and vice versa, the resin is — , but 
the flannel is +. 

149. Electrical Equilibrium. — All cases of electrical ex- 
citement are due to a disturbance of the electrical equilibrium, 
Dr balance of power, which, aside from disturbing causes, 

If wax is used in place of glass, what happens ? What are these 
two electricities called ? 148. What analogy do we see between the 
two electricities and the magnet ? What names do we give to them ? 
Can one sort of electricity exist without the other ? 149. What is 
electrical equilibrium ? 



ELECTRICITY OF FRICTION. 105 

naturally exists among surrounding bodies ; and the intensity 
of the electrical action is directly proportioned to the amount 
of that disturbance. The more unlike in electrical state a 
body becomes to surrounding substances, the more energetic 
will be the display of electrical power. The opposite states 
are, however, always in such proportion as exactly to neu- 
tralize each other in any two substances which have been 
mutually excited, as glass and the silk rubber. 

150. Theories of Electricity. — Two theories have been 
proposed to explain the ordinary phenomena of electricity. 
The first is that proposed by our distinguished countryman, 
Dr. Franklin, (and called the Franklinian hypothesis,) which 
is very simple and ingenious. It supposes that there is a 
simple, subtle, and highly elastic fluid, which pervades all 
matter. This fluid is self-repellent, but attracts all matter, 
or its ultimate particles ; these particles of matter are con- 
sidered as also self- repellent, when deprived of or possessing 
more than their natural quantity of electricity, and as natu- 
rally attracting when they are in opposite conditions. In the 
natural state of bodies, this fluid is uniformly distributed, and 
its increase or diminution produces electrical excitement. 
Accordingly, when a glass tube is rubbed with a silk hand- 
kerchief, the electrical equilibrium is disturbed, the glass 
acquires more than its natural quantity, and is over-charged, 
the silk possesses less, and is under-charged. 

The second hypothesis is that of Du Fay, who conjectured 
that electrical phenomena were due to two highly elastic, 
imponderable fluids, the particles of which are self-repellent, 
but attractive of each other. These two fluids exist in all 
unexcited bodies in a state of combination and neutralization, 
when no electrical phenomena are seen. Friction occasions 
the separation of the fluids, and the electrical excitement in a 
body continues until an equal amount of opposite electricity 
to that excited has been restored to it. 

According to Dr. Franklin's theory, the two states arc 
denominated positive and negative ; according to Du Fay, 
they are distinguished as vitreous and resinous. We can use 
either of these terms indifferently, however, without commit- 
ting ourselves to either theory, both of which cannot be true. 
The real use of such terms is, to enable us to obtain clearer 

150. Name the two theories of electricity. What is the Frank- 
linian hypothesis ? What is Du Fay's view ? What are these two 
theories called ? 



106 ELECTRICITY. 

notions of the relation of the several phenomena ; and the 
hypothesis which they express serves as a thread of phi- 
losophy by which we connect our separate facts. 

151. Conductors and Insulators of Electricity. — The 
pith-balls or glass tubes, which have been electrically 
excited, return to a natural state very slowly indeed, if left 
untouched, in dry air. But the hand, or a metallic rod, will 
at once restore them to the unexcited state, while dry silk, 
glass, and resin, will not remove the excitement. Bodies are, 
therefore, divided into conductors and non-conductors of elec- 
tricity, or, more properly, into good and bad conductors. 
The electrical discharge takes place through good conductors, 
(as the metals,) with an inconceivable velocity, which can 
be compared only to the velocity of light. Among good 
conductors, in the order of their conducting power, are the 
metals, charcoal, plumbago, and various fused chlorids, 
strong acids, water, damp air, vegetable and animal bodies ; 
among imperfect conductors are spermaceti, glass, sulphur, 
fixed oils, oil of turpentine, resin, ice, diamond, and dry 
gases. The latter substances are also called insulators, 
because by their aid we can insulate or confine electricity. 

152. Electroscopes, or Electrometers. — The kind of elec- 
trical excitement in a body is ascertained by a very simple 
apparatus, called an electroscope. The pith-balls (147) 
serve this purpose very well. We excite them by electricity 

of a known kind, as of an excited glass tube 
brought into actual contact with them, and then 
we bring near them the body whose electrical 
state we wish to learn : if they are still further 
repelled, we conclude that the body in question 
has vitreous or positive electricity ; but if they 
are attracted, we conclude that the reverse is true. 
The gold-leaf electrometer is, however, a much 
more sensitive and delicate test of electrical ex- 
citement, and consists of two leaves of gold, 
suspended in arf air-jar, and communicating by a wire with 
a small plate of brass ; the approach to this plate of a body 
in any degree excited, will occasion an immediate movement 
of the gold-leaves, from which we can tell the nature of the 

What is the use of such theories ? 151. What are conductors ? 
What are insulators ? Name some of each. 152. What is an elec- 
troscope ? How do we, by means of it, ascertain the kind of elec- 
tricity ? 




ELECTRICITY OF FRICTION. 



107 



excitement, as above described, having previously imparted 
to the gold leaves a particular kind of electricity. 

153. The Electrical Machine. — The principle of the 
common electrical machine will be easily understood, after 
what has been said. 
Two forms of this 
machine are in com- 
mon use, the cylinder 
and the plate machine : 
a good view of the 
latter is presented in 
the annexed figure ; d 
is a wheel of plate- 
glass, turned on an 
axis by a handle. The 
electricity is excited 
by the friction of two 
cushions or rubbers, 
(e, e,) which press 
against the plate, and 
are covered with a soft 
amalgam of mercury, 
tin, and zinc, which 
greatly heightens the 
effect. The rubbers are connected with the earth by a 
metallic chain, (b.) The excited glass delivers its electricity 
to several sharp points of wire attached to the bright brass 
arms, and connected with the great conductor, (a.) The 
conductor and plate are perfectly insulated by glass supports. 
When thus arranged, and the machine is turned, bright 
sparks of a violet color, forming lines like lightning, will dart 
with a sharp sound to any conducting substance brought near 
to the great conductor. This is positive electricity. If nega- 
tive electricity be wanted, we must insulate the rubbers, and, 
connecting the conductor with the earthy draw the sparks 
from the rubber. 

Every care must be taken in the use of an electrical appa- 
ratus, to keep it clean and smooth, and particularly free from 
moisture. Dust acts as so many points to discharge the 
fluid, and moisture deposits itself in a thin film over the insu- 
lators, and prevents the accumulation of power. 




153. Explain the electrical machine. How is negative electricity 
obtained ? What care is to be used in keeping an electrical machine ? 



108 ELECTRICITY. 

154. The Leyden Jar, or Vial, is the simple means by 
which the experimenter collects and transfers a portion of 
the electricity evolved by his machine, and applies it to the 
purposes of experiment. The Leyden-jar, (so called from 
the place where it was first invented,*) is only a glass bottle, 
covered inside and out with tin-foil up to the line seen in the 

-^ figure. A brass ball communicates by a wire 

Hr and chain with the interior coating, the mouth 

II being stopped by a cover of dry wood. On 

(L^T^ approaching the ball to the conductor of the 

A5pi|L electrical machine, when in action, a series of 

Uwr^B vivid sparks will be received by it, and a great 

"ifff™} accumulation of vitreous electricity takes place 

II SB m tne mter,or > provided the exterior be not 

. | II insulated. On forming a connection by a con- 

illMIL. ductor between the interior and exterior surfaces, 

JUIIfflMB* the equilibrium is at once restored by a rush of 

the opposing forces, accompanied with a brilliant flash of 

artificial lightning, and, if the hand of the operator is the 

conducting medium, a violent shock is felt, commonly known 

as the electrical shock. A series of such jars arranged so 

as to be charged by one machine, is called an electrical 

battery. 

155. The Electrophorusf is a convenient mode of obtain- 
ing an electrical spark, when no 
electrical machine is to be had, 
and consists of a shallow tray or 
dish of tin, (or a wooden box,) 
the size of a dining plate, partly 
filled with melted shellac, (a,) or 
some other resinous preparation, 
made as smooth as possible. A 

disc of brass (b) with a glass handle is provided, and the bed 
of resin is rubbed with a dry flannel or cat-skin ; this excites 
negative electricity and the metal disc is then laid on the 
excited surface, and touched with the finger. A coating of 

154. What is the Leyden-jar, and how used ? 155. What is an 
electrophorus, and how made and used ? 

* This instrument, attributed to one Cunaeus, of Leyden, in 1746, 
has done as much for statical electricity as has the pile of Volta for 
galvanism. 

f From the Greek, electron, and phero, I carry. 




ELECTRICITY OF CHEMICAL ACTION. 109 

positive electricity is induced on it, and it may be raised Joy 
the handle, and discharged by a conductor, giving a vivid 
spark, sufficient to explode gases. The resinous electricity 
not being conducted away from the shellac, the spark may 
be repeated as long as the excitement lasts. Y # 

156. A jet of high steam issuing from a locomotive or 
other insulated steam-boiler, will, with certain precautions, 
give a stream of electrical sparks more powerful than any 
electrical machine. This has been called hydro-electricity, 
and is produced by the friction of the hot steam on the edges 
of the orifice from which the steam issues. 

157. Thunder and Lightning. — These common natural 
phenomena are due to the passage of electricity from one 
cloud to another, or from a cloud to the earth, which is 
usually attended with a brilliant flash and loud explosion. 
Dr. Franklin first suggested and proved the lightning of the 
atmosphere to be the same thing as the machine electricity, 
and contrived an electrical kite by which he drew the lightning 
of the clouds to the earth.* In a thunder-storm the electri- 
cal cloud, the intervening air, and the earth, represent 
respectively the inner and outer coatings of the Leyden-jar ; 
the air being the non-conductor through which the discharge 
finally takes place. 

3. Electricity of Chemical Action. — Galvanism, or Voltaism. 

158. We have found the electricity of friction, or ma- 
chine electricity, to be endued with great energy, passing 
with a vivid spark through a considerable thickness of dry 
air, and capable of being insulated by non-conductors, so as 
to be easily transferred and managed, as in the Leyden-jar. 
Moreover, we know that dryness and insulation from the 
earth are essential to its excitation, by artificial means. 
We shall now see how strongly in these, as well as in many 
other respects, it is contrasted with the sort of electricity 

156. What is said of the electricity of high, steam ? 157. What 
are thunder and lightning ? How are the conditions of a thunder-storm 
like the Leyden-jar '! What was Franklin's discovery about lightning ? 
158. What leading properties have we observed in machine electri- 
city? 

* " Eripuit ccelis fulmen sceptrumque tyrannis." 
10 




110 ELECTRICITY. 

which is the product of chemical action, and best known as 
Galvanism, or Voltaism.* 

159. Origin and Discovery of Galvanism. — Accident led 
to the origin of the science of galvanism in 1790.-)- Gal- 
vanij observed that the freshly prepared legs of a frog were 
convulsed, when brought within the influence 
of a powerful electrical machine in action. 
He at once believed that he had discovered 
in electricity the secret spring of life and 
nervous power. Volta, however, reasoned, 
that the convulsions were in no way con- 
nected with animal life, but that the muscular 
contractions were excited in the legs of the 
frog by induction from the active machine ; 
this effect being produced through the influ- 
ence of two metals, which, at the time, were 
in contact with the naked flesh. This ex- 
periment is easily repeated on the legs of a 
frog, from which the skin has been recently 
stripped. They are suspended by a silver or platinum wire, 
or a wire of any metal, passed under the crural nerves, which 
are easily found, by gently separating the large muscles of 
the legs at a. A slip of zinc, bent so as to touch at the same 
time the toes and the wire of suspension, will occasion violent 
convulsions in the legs. This irritability is lost soon after 
death. 

159. When, how, and by whom, was galvanism discovered ? 
Explain the experiment with the frog's legs. 

* This sort of electrical excitement is, also, frequently called the 
" electricity of contact/' because actual contact of the metals em- 
ployed was supposed to be required. It is likewise called dynami- 
cal electricity, (from dwiamis, power,) and " current affinity." 

f Accident, properly considered, never discovered any philosophical 
principle. The minds of philosophers had been ripening for fifty 
years for Volta's discovery, and the twitching of the frog's legs, like 
Newton's apple, was only the spark which fired the train that had 
been long laid. 

| Prof. Galvani lived at Bologna, in Italy, and Volta of Pavia was 
his nephew and pupil ; although Galvani made the first observations, 
Volta offered the true explanation of the observations of his uncle, 
and by rational experiments supported it against powerful opposition. 
Voltaism would, therefore, seem to be a more just term for the 
science than galvanism.' 



ELECTRICITY OF CHEMICAL ACTION. Ill 

160. Voltaic Pile. — Volta sagaciously reasoned, that the 
same effects could be produced with simple metals and a 
fluid, or substances saturated with a fluid. The truth of this 
conjecture is easily verified, by placing on the tongue a 
silver coin, and beneath it a slip of zinc, or a cent of copper. 
On touching the edges of the two metals so situated, we per- 
ceive a mild flash of light and a sharp prickling sensation, 
or twinge, giving notice of the production of a voltaic cur- 
rent. Volta arranged a series of copper and silver coins in 
a pile, with cloths wet in a saline or acid fluid 
between them. The arrangement is seen in 
the figure. The copper (c) and zinc (z) alter- 
nate with the wet cloth between. The pile 
begins with % and ends with c. On establish- 
ing a metallic communication between these 
extremes by a wire, a current of electricity 
flows in the direction of the arrow on the 
wire.* If one hand be placed on each end 55 -zi 
of the pile, a shock will be experienced, simi- c 
lar in some respects to that from the electrical 
machine, and yet very unlike it. If the pile has many 
members, on touching the wires communicating between the 
extremes, the shock is very intense, and a vivid spark will 
be produced, which is increased if points of prepared 
charcoal are attached to the ends of the wires. The con- 
ducting wires held together will grow hot, and if a short 
piece of small platina wire is interposed, it will be heated 
to bright redness. Such is an outline of the remarkable 
discovery of Volta, whose pile was made known to the 
world in 1800. The principle involved in this arrangement 
is unaltered, although more manageable and extensive forms 
of apparatus have supplied the place of the pile. 

160. What was Volta's reasoning ? What instrument did he in- 
vent, and when? How was it constructed? What is its action? 

* The terms fluid or C7erre?it, are used in obedience to custom ; but 
the learner should remember, that the ' fluid' is only an ideal one, as we 
have no evidence of its existence, and the wire which communicates 
the electrical influence does not carry any fluid, as a pipe carries 
water. There is not a particle of evidence as to the real nature of 
the electrical excitement produced by the action of acid water on 
different metals. All we know is, that so long as such action lasts, 
there is a constant production of an electrical excitement or influence, 
which we call a current. 




112 



ELECTRICITY. 




161. Simple Voltaic Circle. — A voltaic current is 
established whenever we bring two dissimilar metals, (as 
copper, silver, or platina, with zinc or iron,) into contact in 
an acid or saline fluid. Thus if we place a 
slip of copper in a glass of acid water, and be- 
side it in the same vessel a slip of amalga- 
mated* zinc, as long as the two metals do not 
touch there will be no action, but on touching 
the upper ends of the two slips of metal, a 
vigorous action will commence, bubbles of gas 
will be rapidly given off from the copper, while 
the zinc will be gradually dissolved in the acid 
water. This action will be arrested at any moment, on 
separating the two metals. The end of the zinc in the acid 
is -f, or positive, and that in the air — , or negative ; the 
copper has the reverse signs. These relations are expressed 
in the figures by the signs + and — , and by the direction 
of the arrows showing how the + electricity 
of the zinc passes to the — of the copper in 
the acid ; while the bubbles of gas (hydrogen) 
set free at the + end of the zinc, travel over 
and are delivered at the — of the copper. 
The second figure shows how the current 
may be established by wires, without the di- 
rect contact of the slips. In this case the 
wires (as in the pile, 160) carry the influence 
in the direction of the arrows, and the existence of the current 
and its positive and negative characters may be shown by 
the effect produced by it on a small magnetic needle, which 




161. What is a simple voltaic circle? Explain the electrical 
relations of zinc and copper, in and out of the acid. What is 
amalgamation? Is contact of the metals in the vessel necessary ? 
Explain the second figure. What determines the direction of the 
current? 



* Amalgamated zinc, is zinc which has been rubbed over with 
mercury ; this is done by dipping common sheet or cast zinc into a 
dilute acid, and while the surface is still being acted on, rubbing it 
with mercury, which will at once cover the surface with a resplen 
dent surface of quicksilver. Pure zinc does not need amalgamation, 
but all commercial zinc is impure, and the object of the amalgamation 
is to cover over the impurities, (mostly iron and charcoal,) and re- 
duce the surface to perfect electrical uniformity, so that it shall be 
all positive, and not a mixture of positive and negative. 



ELECTRICITY OF CHEMICAL ACTION. 



113 



will be influenced by the wires carrying the current, just as 
by the magnet ; being attracted or repelled according as it 
is above or below the wire, and in either case endeavoring 
to place itself at right angles to the conducting wire, (166.) 
The direction of the voltaic current (and of course the -f 
or — qualities of the metals from which it is evolved) de- 
pends entirely on the nature of the chemical action produced. 
Thus, if in the arrangement just described, strong ammonia 
were used, in place of the dilute acid, all the relations of the 
metals and the fluid would be reversed, since the action 
would then be on the copper. The chemical effects of the 
voltaic circle will be considered in the chapter on chemical 
philosophy. 

162. The Compound Voltaic Circle. — If, in place of one 
cell, as just described, we arrange several of the same sort, 
like the three in the 
figure, not forming 
any direct metallic 
communication be- 
tween the members 
of the same cell, but 
only between those 
of different cells, 
then we shall find 
(attending to the signs + and — ) that the positive electricity 
of the first copper will be exactly neutralized by the nega- 
tive of the zinc of the next cell, and so on ; and we shall 
have at the terminal wires only the same quantity of elec- 
tricity which we had in a single cell ; all the opposite 
electricities of the intermediate members being exactly 
neutralized.* 

163. Quantity and Intensity. — We learn the remarkable 
fact from this statement, that, no matter how much we may 
increase the number of the members in the voltaic circle, the 
qua/itity of electricity passing in the current is equal only 




If ammonia were used, how would it be ? 162. What is a com- 
pound voltaic circuit ? How are the members united ? Explain 
the relations from the signs -f- and — . What do we thus dis- 
cover ? 



* This form of apparatus was called the crown of cups, (Courojinc 
dc tasses,) being arranged in a circle. 
10* 



114 '• ELECTRICITY. 

to that evolved by a single cell. But the current which has 
passed through a number of similar cells has acquired an 
intensity exactly proportioned to the number. Thus no 
single cell, however large, would ever afford electricity of a 
tension sufficiently high to decompose water, or give the 
slightest shock to the animal frame. But the increase of 
size of the individual plates will enable us to produce much 
greater effects of induced magnetism, and to accumulate 
heat to a surprising extent.* These effects are said to 
depend on the quantity of electricity, while the other class 
depend on greater intensity given to a smaller amount of 
electricity, by extending the series. 

The electricity always flows, both in simple and compound 
circles, from the zinc to the copper, in the fluid of the battery ; 
and from the copper to the zinc, out of the battery. This is 
important to be remembered, since the zinc is called the 
electro-positive element of the voltaic series, although out of 
the fluid it is negative ; and consequently, in voltaic decom- 
position, that element which goes to the zinc pole is called 
the electro-positive element, being attracted by its opposite 
force ; while the element going to the copper is called, for 
the same reason, the electro-negative. The compound 
circle, reduced to the simplest form of expression, would 
be— 

Copper — zinc—Jluid — copper — zinc. 

Here the copper end is negative and the zinc positive 
but the two terminal plates are in no way concerned in 
the effect ; so that, throwing them out of the question, 
we bring it to the state of the simple circle, which is 
simply — 

. Zinc— fluid — copper ; 
and here we find the zinc end negative, and the copper end 
positive. 



163. Explain what is meant by quantity and intensity. What ad- 
, vantage is there in multiplying the series, if no more electricity is 
evolved ? What happens from the use of large plates ? How does 
the current always flow in the battery ? How out of it ? What 
electrical names then have the copper and zinc ? Reduce the com- 
pound circle to its simple form of expression. 



* Hare's calorimotor^ or heat-mover, is constructed on this 
principle. 



ELECTRICITY OF CHEMICAL ACTION. 



lib 




164. Galvanic batteries are very various in form, but all 
involve the same principle. Besides those already men- 
tioned, we may briefly name a few others; and, (1,) Mr. 
Cruickshank's, called the p^=^==^= 
"trough battery," is [ ^SlllSSlL 
formed of double plates 
of copper and zinc sol- 
dered together, and cemented into a mahogany trough, so 
as to form a series of tight cells, into which the acid fluid is 
poured ; the effect is greatest at the first moment of contact 
of the acid and plates, 
and the operator must 
hasten to complete his 
experiments before the 
power has materially de- 
clined. (2.) To avoid 
this inconvenience, Dr. 
Wollaston contrived the 
annexed arrangement, 
where the copper is bent 
so as to surround the 
zinc, thus doubling the 
surface compared with 
the last ; the metallic 
connections are made to a bar of wood, by means of which 
the whole series may be easily raised and lowered, in the 
porcelain or earthen-ware trough, having a separate cell for 
each pair. 

(3.) Dr. Hare, of Philadelphia, first informed us that 
separate cells were not required for each pair of plates, and 
that by packing an arrangement similar to Wollaston's, in a 
frame, with varnished paste-boards between the members, 
to prevent any metallic contact, a large number of members 
might be instantaneously immersed and raised again from 
the acid fluid at one movement. The greatest economy of 
power is thus gained, and the effects are truly surprising. 
Such an arrangement is called a dcflagrator, from the energy 
with which it deflagrates or burns the metals and other 
combustible substances. There is a battery of this kind in 
the Laboratory of Yale College, consisting of nine hundred 




164. Mention some of the forms of battery. (1.) Cruickshanks', 
and-its .disadvantages. (2.) Wollaston's improvement. 



% 




116 ELECTRICITY. 

members, 4x12 inches, each zinc being surrounded by^i 
copper case, and the whole packed as above described in 
twelve frames, and all immersed at one movement. The 
fluid used to excite this battery is usually dilute sulphuric 
acid, (1 part acid to 14 or 16 of water by weight.) Its 

deflagrations are ex- 
tremely splendid and 
energetic, and the arch 
of light (A in the an- 
nexed figure) given 
out at its poles, be- 
tween points of char- 
coal, (C C,) has often been five or six inches in length. The 
power of such an instrument in chemical decomposition is 
very great. 

There are many other forms of voltaic battery, but we 
have not space to mention any more, except those which 
will be named when we treat of the chemical effects of 
galvanism. As more knowledge of chemical terms than the 
student is now supposed to possess would be required to 
make them intelligible, they are described under the head of 
chemical philosophy. 

165. Effects of Voltaic Electricity. — These are con- 
veniently classified under the heads, (1,) Electrical, (2,) 
Luminous, (3,) Calorific, (4,) Electro-magnetic, (5,) Chemi- 
cal, (6,) Physiological. Of these, the first three and the last 
have received as much attention as our limits will permit. 
The fifth will be considered after we have become somewhat 
familiar with the principles of chemical philosophy. We 
have then to consider, briefly, the fourth effect of voltaic 
electricity, 

Electro-Magnetism. 

166. If a wire conveying a voltaic current is brought 
above, and parallel to, a magnetic needle, (as shown in figure 
a,) the latter is invariably affected, as if the poles of another 
magnet had been brought near, (139.). If the current is 



(3.) Hare's deflagrators, and their great superiority. 165. How 
are the effects of voltaic electricity classed? 166. How is the mag 
netic needle affected by the voltaic current ? 



ELECTRO-MAGNETISM. 



117 



db~ 




flowing, as indicated by the arrow on the 
wire, say to the north, then the north •pole 
of the needle will turn to the east; if 
the current is flowing south, it will turn to 
the west. If the line carrying the current 
is placed beneath the needle, the same effect 
is produced as if the current had been re- 
versed ; the needle turns in the opposite 
way to what it does when the wire is a 

above. The effort of the needle is to place itself at right 
angles to the wire, as if influenced by a tangential force. 
If the wire is bent in a rectangle, as in 
iigure b, and wound with silk or cot- 
ton, to prevent metallic contact, and 
the lateral passage of the current 
from wire to wire, then it is evident 
that any current which may be flowing 
over the wire will have to pass com- 
pletely around the needle, and the effect which is produced 
will be in proportion to the number of turns made by the 
wire, since its influence is multiplied by the number of turns. 
In this way we can make a very feeble current give decided 
indications. Prof. CErsted, of Copenhagen, in 1819, first made 
known the law of electro-magnetic attraction and repulsion ; 
since which time the progress of this branch of science has 
been very rapid. 

167. Galvanoscopes, or (Galvanometers, are instruments 
by which we measure the force and direction of a galvanic 
or voltaic current, which is often a most 
important thing to be known. The prin- 
ciple of the last arrangement is here ap- 
plied. In order to free the magnetic 
needle from the directive tendency which 
it receives from the earth's magnetism, 
two needles are used, with their unlike 
poles placed opposite to each other, (see 
fig. a,) one within and the other above 
the coil. They will then hang suspended 
by the silk fibre which supports them, 



What is the effect of the needle ? If the wire is bent into a rect- 
angle, what is the effect ? Who discovered the first law of electro- 
magnetism, and when ? 167. What are galvanoscopes ? 



118 



ELECTRICITY. 



with no tendency to swing in any direction, since they are 
wholly occupied with their own attractions and repulsions, 
and their directive power is neutralized ; consequently, they 
are free to move with the slightest in- 
fluence of any current passing through 
the coil. Such an arrangement is called 
an astatic needle.* To give it greater 
delicacy, and prevent the currents of air 
from moving it, a glass shade (fig. b) 
is placed over it, and the movements of 
the needle are read on the graduated 
circle.f For the purpose of elementary 
explanation of the principles of electro- 
magnetism, such a needle as that figured 
in the last section will answer. The 
tendency of the galvanometer-needle, 
it will be remembered, is always to 
place itself at right angles to the direc- 
tion of the electrical current, that position being the equator 
of the attracting and repelling powers, and consequently a 
point of equilibrium. 

168. Ampere's Theory. — The discovery of the first law 
of electro-magnetic influence by (Ersted, attracted great 
attention; and in 1820, M. Ampere, a French philosopher, 
made the suggestion that the magnetism of the earth was due 
to the influence of the sun's rays, which, falling on the earth, 
might be considered as encircling it in an unending series of 
spiral lines, producing in it the phenomena of magnetic in- 
duction, (140.) The discovery, by CErsted, of the magnetic 
influence of an electric current, (166,) led him to conjecture, 
that if such a current was made to pass in a spiral about any 
conductor, it would become magnetic. This idea led to the 
discovery of the phenomena of the 

169. Helix.\ — A wire coiled in the form here represented, 




Explain the figures. 
Ampere's theory. 



What is an astatic needle ? 168. State 



* From the Greek, astatos, just balanced. 

f It was a galvanometer such as this which was referred to as being 
used in Melloni's apparatus, (104.) 

| So called from the Greek, kelisso, to twist round ; Latin, helix 3 
in allusion to the coiling of a vine about a tree. 



ELECTRO-MAGNETISM. 



119 




and made the medium of communication for a voltaic current, 
becomes capable of manifesting 
very strong magnetic influence 
on any conductor placed in its 
axis. A delicate steel needle, 
laid in the helix, will be drawn 
to the centre and held suspended 
there, without material support, like Mahomet's fabled coffin. 
If the needle is of steel, the magnetism it thus receives will 
be retained by it ; but if it be of soft iron, it is a magnet only 
while the current is passing ; brass, lead, copper, or any 
other metallic conductor, can in this way be made to mani- 
fest temporary magnetic power. The more closely the helix 
is wound, and the more revolutions it makes, the more pow- 
erful is the magnetism which it can induce, (166.) It is 
essential that the wire of which it is formed should be insu- 
lated from contact with itself, by being wound with silk or 
cotton, or coiled in an open spiral, as in the figure. A short 
and stout wire of lead or copper, connecting the poles of a 
single ^cylinder battery, when excited, becomes strongly 
magnetic, as may be seen by the bundle of iron-filings which 
it will then attract ; each filing becomes itself a magnet, and 
the whole surround the wire in a beautiful tuft or festoon. 
The moment the connection between the poles is broken, 
they all fall, and the wire has not power to lift a single par- 
ticle of iron. 

170. De la Rive's Ring. — We infer, therefore, that the 
helix itself has polarity, and this is beautifully proved by the 
arrangement represented in the an- am 
nexed figure, called De la Rive's 
ring, which is simply a small wire 
helix, whose ends are attached to the 
little battery of zinc and copper con- 
tained in a glass tube, and the whole 
made to float on the surface of a 
basin of water, by means of a large 
cork, through which the glass tube is thrust. On exciting 
this small battery by a little dilute acid, poured into the 




169. What discovery did Ampere's theory lead to ? What is a 
helix, and its action? How does a stout wire in the poles of a bat- 
tery show the spiral or tangential direction of the current ? 
170. What does De la Rive's ring show ? Explain it. 



120 ELECTRICITY. 

tube, and placirg the apparatus on the water, it will at once 
assume a polar direction, as if it were a compass-needle, the 
axis of the helix being in the magnetic meridian ; and it will 
then obey the influence of any other magnet brought near it, 
manifesting the ordinary attractions and repulsions. 

171. Electro-magnets. — We may avail ourselves of the 
principle of the helix to manufacture artificial magnets ; if 
steel wires are introduced, as before stated, (169,) within the 
helix, they become permanent magnets, while soft iron is 
made only temporarily so. The position of the poles may 
be determined by a little reflection from what has been 
already said. If the helix is wound from left to right, the 
poles will be the reverse of their position if the winding was 
from right to left : a reversal of the direction of winding will 
be the same as changing the poles. By reversing the wind- 
ing in the middle of the helix, we shall establish two sets of 
poles ; and if it is twice reversed, three sets will be pro- 
duced, and so on ; we can also reverse the polarity of our 
magnet at will, by changing it end for end in the helix, or 
by reversing the direction of the current. 
Obvious as was the conclusion to which 
these principles lead, Prof. Henry, of Prince- 
ton, was the first who attempted to apply them 
to the production of large magnets, from soft 
iron wound with successive short coils of 
covered wire, as in the figure. In this way, 
he succeeded in producing the most powerful 
magnets which have been made. One on 
his plan, now in the Laboratory of Yale 
College, has lifted 2500 pounds. In these 
magnets the wire is insulated, and wound in 
short coils of 60 to 100 feet, the opposite 
ends of which are connected with the oppo- 
site poles of the battery. A small battery 
was used in one of his experiments, consisting of two con- 
centric cylinders of copper soldered into a cup, to hold half 
a pint of dilute acid, with a zinc cylinder immersed in it. 
With this, 650 pounds were sustained by the magnetism 
induced in a bar of soft iron, two inches square, twenty 



171. How is the principle of the helix applied to making artificial 
magnets ? If the helix is reversed ? If twice reversed ? Mention 
Prof. Henry's magnets. How much have they been made to lift ? 




ELECTRO-MAGNETISM. 



121 



inches long, and bent into the horse-shoe form. This was 
wound with 540 feet of insulated copper bell-wire, in nine 
separate coils of 60 feet each. With, a larger battery, the 
same magnet sustained 750 pounds. A very small electro- 
magnet has been made to lift 420 times its own weight. 

172. The Magic Circle. — The reader must remember 
that the magnetism of soft iron, induced from the voltaic 
current, is not the result of contact between 

the helix or coil and the iron ; but this effect 
is produced through an intervening space 
of air, or other material which is non-con- 
ducting to ordinary electricity, or galvan- 
ism. The annexed figure shows two small 
semicircles of soft iron, forming a ring 
when united, and fitted with handles ; a 
small coil of insulated wire, (R,) placed 
within the soft iron circle, will cause the 
induction of magnetism in it, the moment 
the terminal wires (a b) are connected 
with a small battery. The rings of iron 
and of wire are quite distinct, and may be 
moved about in each other ; the soft iron 
semicircles seem bound together as if by 
magic, and hence the apparatus has been 
called the magic circle. Fifty or sixty 
pounds are easily sustained by such an 
apparatus made of iron about half an inch 
in diameter. 

173. Electro-Magnetic Motions. — The great magnetic 
power induced in soft iron, early suggested its application 
to the moving of machinery. As yet, however, we have 
produced nothing which can take the place of steam or 
water, as a moving power. The causes of failure cannot 
well be explained in this place, as they involve some chemical 
reasoning which would be in anticipation of our knowledge. 

Faraday was the first who succeeded in producing mo- 
tion by the mutual action of magnets and conductors. It is 
quite impossible to name, much less describe, even a tenth 




172. Is electro-magnetism the result of contact ? Illustrate this 
from the magic circle. 173. Has the great power of electro-magnets 
been made available for use ? Who first produced electro-magnetic 
motion ? 

11 



122 



ELECTRICITY. 



part of the ingenious and instructive forms of apparatus 
which have been contrived by various experimenters, for 
producing motion. 

Ampere's Rotating Battery is an instructive form of appa- 
ratus, and one of the first contrived. 
In this, a small double cylinder or cup 
of copper is hung by a pivot over and 
around the pole of a U magnet, standing 
as represented in the sectional figure on 
pole S. This holds the dilute acid, into 
which the zinc cylinder (Z) dips, which 
is suspended on another pivot so as to 
hang freely. As soon as the acid 
water is poured into the cup, a current 
of electricity will flow (161) from the 
zinc to the copper, over the wire and 
through the pivot to the zinc again. 
The zinc and copper are in the con- 
dition of two conductors, conveying 
an electric current in opposite direc- 
tions, and being under the influence 
of the poles of the magnet, (166,) and 
free to move, they revolve in opposite 
directions. If each pole is thus provided, the cups and zincs 
on each will revolve differently. 

174. Page's Revolving Armature* — One of the simplest 
forms of the electro-magnetic engine is that figured on the 
next page, in which an electro-magnet (M) is fixed on a stand, 
with its poles in an upright position. A brass wheel is so 
placed over it, that three bars or armatures of soft iron, (A,) 
which divide the circumference, may pass very near to the 
poles of the magnet, as the wheel turns. The arrangement 
is such, that the revolution of the wheel shall break the 




Describe Ampere's rotating battery. 174. What is Page's re- 
volving armature, and how does it operate ? 



*Dr. C. G. Page of the Patent Office, Washington, is the author of 
numerous ingenious electro-magnetic machines, [for an account of 
which see the American Journal of Science, passim,] and is one of the 
most successful cultivators of this science. His apparatus, with 
much other useful matter, will be found described and figured in a 
useful work called Davis's Manual of Magnetism, 18mo. Boston, 
1842. Several of the figures here given are from Mr. Davis's book. 



ELECTRO-MAGNETISM. 



123 



connection between the battery and the electro-magnet, 
three times in every revolution. This is accomplished by 
the wire (B) which plays upon three 
pins of wire, in the little disc seen 
upon the horizontal axis of the 
wheel. As often as these pins 
touch the wire, (B,) the circuit is 
completed, and the soft iron (M) 
becomes a magnet. As soon, how- 
ever, as this contact is broken, M 
ceases to be a magnet. Now this 
happens three times in every revo- 
lution of the wheel, and the breaking 
of contact is so contrived that it 
always happens just when one of 
the soft iron armatures (A) comes 
over the poles of the electro-magnet. 
The bars (A) being each in suc- 
cession strongly attracted to the 
poles of the magnet, cause the wheel 
to move, and the revolution, being 
once established, is kept up with 
great velocity. If the magnetism in 
M was not destroyed by the contact- 
breaker, (B,) at the very time when A comes over the poles 
the revolution would be arrested by the strong attraction of 
the magnet for the armature. 

175. Henry^s Coils. — When an electrical current from 
a single pair of plates is passed through a long conductor, 
as a spiral of copper ribbon, or a long bell-wire, it will be 
found, at the moment of breaking the contact between the 
conductor and the battery, that vivid sparks will appear, and 
a feeble shock will be felt if the moistened fingers grasp the 
naked conductors. 

A long conductor then supplies the place of an increased 
number of plates in a voltaic series, and to some degree 
imparts the quality of intensity (163) to a current of quan- 
tity. A flat spiral of copper ribbon one hundred feet long, 
wound with cotton, and varnished, shows these effects well. 
A magnetic needle will be powerfully affected by this coil 
while the current is passing ; the N. or S. pole being drawn 




175. What is the effect of Henry's coils on the voltaic curr.ent ? 




124* ELECTRICITY. 

toward the centre, (see the figure,) according to the direction 
of the current, the reversal of the 
current producing a reversal in the 
direction of the needle. The oppo- 
site sides of the spiral of course 
produce opposite effects on the 
needle. Its axis, it will be seen, is 
the same as that of the helix,. 
(169,) and it will in like manner j 
produce magnetism. The mag- 
netism is, however, to be distin- 
guished from the new effects excited by the passage of the 
feeble current through the coiled conductor, on breaking con- 
tact, i. e., the vivid spark and the shock. The latter is feeble 
with 100 feet of copper ribbon, and becomes more intense 
(178) if the length of the conductor be increased, the battery 
remaining the same; but the sparks are diminished by 
lengthening the conductor. The increase of intensity in the 
shock is, however, limited by the increased resistance or 
diminished conduction of the wire, which finally counteracts 
the influence of the increasing length of the current. On the 
other hand, if the battery power be increased, the coil remain- 
ing the same, these actions diminish. This class of phe- 
nomena has been attributed to the induction of a current 
upon itself. Prof. Henry first observed the effects here 
described, and has made an extended series of researches on 
this species of induction, as well as that mentioned in the next 
section. 

176. Secondary Currents. — If a long coil of fine insulated 
wire be brought within a small distance of the flat spiral, 
figured in the last section, a new species of induction will be 
detected in the coil of fine wire. The arrangement used by 
Prof. Henry is seen in the annexed figure. A small sus- 
taining battery (L) is connected with the flat spiral of copper 
ribbon, (A,) by wires from the battery cups, (Z and C.) 
This communication is broken at will, by drawing the end 
of one of the battery wires (Z) over the rasp on the spiral. 
When the coil of fine wire (W) is in the position indicated 

What does the long conductor imitate ? How is the magnetic 
needle affected by the flat spiral ? How are the two effects of shock 
and spark related to the length of the conductor ? To what are 
these effects attributable ? 176. What are secondary currents ? 
Explain the arrangement here figured, and the effects. 



ELECTRO-MAGNETISM. 



125 



in the figure, and the hands grasp the conductors at the ex- 
tremities, a violent shock is felt by the person holding the 




conductors, as often as the circuit is broken by the passage 
of the wire over the rasp. When the coil (W) contains 
several thousand feet of wire, the shocks are too intense to 
be borne. As this induction takes place through an inter- 
vening space of air, or non-conductors, we can, by placing 
the spiral (A) against a division wall or the door of a room, 
give shocks to a person in another room, who grasps the 
conductors of the wire coil, (W,) and brings it near to the 
wall on the side opposite to A. This effect is produced 
as if by magic, without a visible cause. A screen or disc 
of metal introduced between the two coils will cut off this 
inductive influence, by itself becoming the medium of an in- 
creased current. But if it be slit by a cut from ^. .. 

the centre to the circumference, as a b in the Q^ J* ^j 
figure, the induction of an intense current in W ^=v===s=s^ 
is the same as if no screen were present. Discs or screens 
of wood, glass, paper, or other non-conductors, offer no im- 
pediment to this induction. 

177. Induced currents of the third, fourth, and fifth 
order. — If the wires from W be connected with another flat 
spiral, and it with a second coil of fine wire, and so on, a 
series of currents will be induced in each alternation of coils. 
The secondary intense current in B, will induce a quantity 
current in the second flat spiral, (C ;) and a second fine wire 
coil (W) will induce a tertiary intense current, and so on. 
These currents have been carried to the ninth order, de- 
creasing each time in energy by every removal from the 



When is the shock felt by the person holding the ends of the fine 
wire ? What magical modification of the experiment is mentioned ? 
How do screens of metal affect the induction ? How, if they are 
slit ? How, if of non-conducting substances ? 
11* 



126 



ELECTRICITY. 



original battery current. The polarity, or direction of these 
secondary currents, alternates, commencing with the sec- 




ondary. Thus the current of the battery is + ; and the 
secondary current is -f ; the current of the third order is — ; 
the current of the fourth order is + ; and the current of the 
fifth order is — . These alternations are marked in the figure 
above. 

178. Compound Electro-magnetic Machine. — By com- 
bining and modifying the results just briefly enumerated, a great 
number of ingenious and beautiful electro-magnetic machines 
have been produced, founded on the principle of the flat spiral, 
secondary intense currents, and induced magnetism. One of 

these, contrived by 
Dr. Page, is figured 
in the margin. In 
this little machine, a 
short coil of stout in- 
sulated copper wire 
forms a helix, within 
which some straight 
soft iron wires (M) 
are placed. The bat- 
tery current is made to pass through this stout wire, by which 
means magnetism is induced (169) in the soft iron. The 
conducting wires are so arranged beneath the board, that the 
glass cup (C) containing some mercury is in connection with 
the battery. The bent wire (W) dips into this mercury, and 
also by a branch into B, and when in the position shown in 




177. Explain the induced currents of the third, fourth, and fifth 
or'<er, and their several polarities. 178. How are the principles of 
175 and 176 combined in the instruments here figured ? Where is 
the magnetism ? 



ELECTRO-MAGNETISM. 127 

the figure, the current from the battery will flow uninter- 
ruptedly. As soon, however, as the battery connection is 
completed, M becomes strongly magnetic, and draws to itself 
a small ball of iron on the end of P; this moves the whole 
wire (P W) and raises the point out of the mercury, (C ;) as 
the wire leaves the mercury, a brilliant spark is seen on its 
surface, (176 ;) the contact being thus broken with the bat- 
tery, M ceases to receive induced magnetism, and the ball 
(P) being consequently no longer attracted to M, the wire 
(W) falls by its gravity to the position in the figure. This 
again establishes the battery connection, and the same effects 
just described recur ; thus the bent wire (W) receives a 
vibratory motion, and at each vibration a brilliant spark is 
seen at C, and M becomes magnetic. It remains only to 
mention that the short quantity wire is surrounded by a fine 
intensity wire, 2000 to 3000 feet long, having no metallic 
connection with the battery or quantity wire, with its ends 
terminating in two bindinsr screws on the left of the board. 
The fine wire receives a secondary induced current like the 
coil, (W, 176,) which, if touched, produces the most intense 
shocks at each vibration of the wire. 

179. The Electro-magnetic telegraph is a contrivance 
which very happily illustrates the application of abstract 
scientific principles and discovery to the wants of society. 
The inconceivably rapid passage of an electrical current over 
a metallic conductor, was discovered by Watson in 1747, 
and this discovery gave the first hint of the possibility of 
using electricity as a means of telegraphic communication. 
Numerous attempts were made very early after this discovery 
to construct a telegraph to be worked by ordinary electricity, 
but from difficulties inherent in the mode, these attempts were 
attended with only very partial success. The discovery of 
electro-magnetism by Oersted, in 1820, (166) supplied the 
necessary means of successful construction. Many plans 
have since been proposed for accomplishing this object, most 
of which have failed from a want of simplicity in construction 
and notation, and from consequent inefficiency. Superior to 
all others in these essential conditions of success, is the beau- 
tiful contrivance patented by Prof. Morse in 1837, which we 
will now briefly describe. 

When is the spark, and when the shocks 1 179. What suggested 
the electrical telegraph ? What discovery gave the means of success ? 



128 



ELECTRICITY. 



The successful operation of the electric telegraph depends 
on the fact, that an electro-magnet can be created at any 
point, no matter how distant from us, provided a good metallic 
communication is established by conducting wires between 
the battery and the distant station. There is no difficulty in 
understanding how the power of the battery on our table may, 
by long wires, be made to move any electro- magnetic ma- 
chine on the other side of the room, or in an adjoining apart- 
ment. We have only to extend this idea to places distant 
from each other, 100, or 1000, or 10,000 miles, and we have 
a conception of the magnetic telegraph. The machinery 
required is of the simplest kind. In the accompanying figure 




u 1 

we have a view of its most essential parts. It is called the 
telegraphic register. A simple electro- magnet, (m m,) with 
its poles upward, receives its induced magnetism (171) from 
a current of electricity conducted by the wires (W W) from 
the distant station. Suppose that the battery which excites this 
current is in Washington, and the electro- magnet is in Boston. 
As soon as the circuit is completed by the union of the poles 
in Washington, m m becomes a magnet, and draws to its 
poles an armature or bar of soft iron (a) on the lever, (I.) 
The motion of this lever starts a spring which sets in motion 
the clock arrangement, (c.) This clock machinery, in con- 
sequence of the weight attached to it, will, when once set in 



On what does the operation of the telegraph depend ? 
apparatus as here figured. 



Explain the 



ELECTRO-MAGNETISM. 129 

As soon as it begins to move, the 
bell (b) is rung by the machinery, to warn the superintendent 
that he is about to receive a communication. The immediate 
object of the clock machinery is to draw forward a narrow 
ribbon of paper, (p p,) in the direction of the arrows, and to 
cause it to advance with a regular motion. The paper ribbon 
passes by the end of the pen lever, (Z,) in which is a steel 
point, (s,) that indents the paper whenever this end of the 
lever is thrown upwards by the attraction of the armature (a) 
to the magnet, (m.) Ifmm were constantly magnetized, the 
mark made by the point (s) would be a continuous line. But 
we have before seen that we can make and discharge an 
electro-magnet as often and as fast as we please ; the instant, 
therefore, the circuit (w w) is broken by the operator at the 
battery in Washington, m m ceases to be a magnet, and lets 
go the iron armature, (a,) when the point (s) of the lever 
falls, so as no longer to mark the paper. The circuit being 
renewed, the point marks again ; and this may be repeated 
as often as the operator at Washington pleases. The length 
of time that the circuit is closed, will be exactly registered in 
the corresponding length of the mark made by s. The com- 
pleting of the circuit is performed by touching a spring on 
the operator's table, which establishes a metallic communi- 
cation between the poles of the battery. A touch will pro- 
duce a dot, a continued pressure a long line, and intermitting 
repeated touches a series of dots and short lines. This 
enables the operator to mark the paper at Boston with a 
series of dots and lines, so arranged as to form a telegraphic 
alphabet, by means of which he can easily and rapidly com- 
municate his thoughts. To complete the arrangement, the 
operator in Boston must have his own battery in connection 
with another similar register in Washington. In practice 
only one wire is used with each register, the circuit being 
completed by connecting the other pole of the battery with 
the moist earth by means of a buried metallic plate and a 
wire. The remarkable observation that the earth could be 
used in this manner as a part of the circuit, was made by 
Steinheil, in Germany, in 1837. Such is a brief account of 
one of the most remarkable discoveries of modern times; 



What is the object of the clock-work ? How does the point mark 
the paper ? What relation is there between the length of the marks 
and the battery circuit ? How are the conducting wires arranged ? 



130 



ELECTRICITY. 



many particulars are purposely omitted, to avoid confusion in 
the main idea. The paper ribbon (p) is supplied from a 
large coil not shown in the figure. This telegraph makes a 
permanent record of the communication sent, and is thus 
independent of the presence or attention of the attendant. 
If it were possible to unite the antipodes by telegraphic wires, 
no measurable time would be required to make communi- 
cations, such is the inconceivable rapidity of electrical 
currents. 

One curious fact connected with the operation of the tele- 
graph, is the induction of atmospheric electricity upon the 
wires to such an extent, as often to cause the machines at 
the several stations to record the approach of a thunder-storm. 
This induction occasions a serious inconvenience in working 
the telegraph, not unattended with danger to the operators. 
The electricity thus induced on the wires may, however, be 
withdrawn by points of metal in communication with the earth, 
and placed at a suitable distance from the conductor. 

180. Magneto- Electricity. — As we have seen effects pro- 
duced from galvanism, which exactly resemble those of ordi- 
nary machine electricity, and the magnetic influence, so, 
conversely, we might expect the production of electrical effects 
from the magnet. The electrical current from a single 
galvanic pair, we have seen, produces magnetism in a spiral 
wire at right angles with its own course ; so the induction of 
magnetism in soft iron from a permanent magnet, in like 




What is said of the atmospheric electricity ? 
neto-electricity ? 



180. What is mag- 




THERMO-ELECTRICITY. 131 

manner, produces an electrical current at right angles to itself 
in the wire coiled on the armature. This class of phenomena 
was discovered hy Faraway in 1831, and our countryman, 
Mr. J. Saxton, soon contrived a machine very similar to the one 
of which a figure is here given, called a Magneto-electrical 
Machine. This consists of a powerful magnet, (S,) secured 
to a board, with its poles so situated that an armature, formed 
of two large bundles of insulated copper wire, (W,) wound 
on soft iron axes, may be revolved on an axis before its 
poles, by the multiplying wheel, (M.) A current of electricity 
is thus induced in W, just as in the flat coils, the permanent 
magnet here taking the place of the flat spiral, (176.) The 
current excited in W is led off by conductors to the binding 
screws, (p and n,) the continuity of the current being broken 
(in imitation of the rasp in 176) by a contrivance at 
b on the axis, called a break-piece, which is made 
by alternate ribs of metal (c) and ivory (i) as in 
the annexed figure; the current is broken by the 
ivory and renewed by the metal, and at every break the per- 
son whose hands grasp the conductors secured to p and n 
feels a sharp shock, which may be graduated at will by the 
rapidity of the revolutions of M, and by the adjustment of the 
break, (b.) A long and fine wire — say 3000 feet of wire -Jg- 
of an inch in diameter — is required to produce shocks and 
chemical decompositions. A shorter and stouter wire, as 250 
feet of wire T *g- or -^ inch in diameter, will produce no shock, 
but will deflagrate the metals powerfully, and produce a 
secondary current of induction in soft iron. We thus imitate in 
magnetism the effects produced from a voltaic current, (163 ;) 
the short and stout wire of the armature is the simple circuit 
of large plates; the long and fine wire is like the com- 
pound circuit of smaller plates. 

4. Ther mo-Electricity, or the Electrical current excited 
by Heat. 

181. If two metals unlike in crystalline structure and 
conducting power are united by solder, and the point of their 
union is heated or cooled, an electrical current will be ex- 

Who discovered this class of phenomena, and when ? What is 
magneto-electricity the converse of? Explain Saxton's machine. 
Explain the relations of the quantity and intensity wire to the simi- 
lar effects of the voltaic battery. 





132 ELECTRICITY. 

cited, which will flow from the heated point to the metal 
which is the poorer conductor. Bismuth and 
antimony are such metals, being bad conduc- 
tors, and unlike in crystalline structure. If 
two bars of these metals are united, as in the 
figure, and the point (e) is warmed by a lamp, 
a current will be set in motion which will flotf 
from b to a, as in the figure. The compas: 
needle may be thus affected, as by the voltaic 
current, (166.) For this purpose two bars may be mounted 
as in the figure, and their j'.nction 
being heated by a lamp, the needle 
will swing, in consequence of the 
electrical current exci<id by the heat. 
When several such are joined, we 
Jp*' have a greatly increased effect, as 
i"'ii"»ii!lr will be remembered in the thermo- 
electric pile in Melloni's apparatus, (104.) 

Thermo-electric effects are not col fined to metals, for they 
may be produced from other solids, and even from fluids ; and 
a single metal, as an iron wire, which has been twisted or bent 
abruptly, will originate a thermo-electric current when the 
distorted part is greatly heated. The rank of the principal 
metals in the thermo-electric series is as follows, beginning 
with the positive: bismuth, mercury, platinum, tin, lead, 
gold, silver, zinc, iron, antimony. When the junction of 
any pair of these is heated, the current passes from that 
which is highest to that which is lowest in the list, the ex- 
tremes affording the most powerful combination. 

If we pass a feeble current of electricity through a pair of 
antimony and bismuth, the temperature of the system rises, 
if the current passes from the former to the latter ; but if 
from the bismuth to the antimony, cold is produced in the 
compound bar. If the reduction of temperature is slightly 
aided artificially, water contained in a cavity in one of the 
bars may be frozen. Thus we see that as change of tempe- 
rature disturbs the electrical equilibrium, so conversely the 
disturbance of the latter produces the former. 

181. What is thermo-electricity ? In what substances is it ex- 
cited ? What metals are here named ? Which way does the current 
flow ? Are these effects confined to metals ? Are two metals 
essential ? Enumerate the order of some metals producing thermo- 
electric effects. What experiment is stated the converse of the 
foregoing ? 



CHEMICAL PHILOSOPHY. 133 

PART II.— CHEMICAL PHILOSOPHY. 

I. ELEMENTS AND THEIR LAWS OF COMBINATION. 

182. Number and Classification of Elements. — We have 
already defined the chemical sense of the word Element, 
(14,) and mentioned that there are fifty-six such substances 
at present known to us. There are also several other sub- 
stances which have been lately proposed as elements of the 
metallic class, — about which, however, we know so little, 
that they are not included in our list, (188.) About forty 
of the elements have the peculiar lustre, and other properties 
of metals, and it is customary to divide the elements into two 
great classes — the metallic and the non-metallic. This con- 
venient distinction is not, however, strictly accurate, since 
there are several elements which, like tellurium, carbon, 
arsenic, silicon, &c, seem to possess an intermediate 
character. Only fourteen of the elementary bodies are of 
common occurrence, and of these the atmosphere, water, and 
the great bulk of the planet are composed. The remainder 
are comparatively rare,' and are known only to the chemist. 
But the same laws of combination apply to the whole, and 
we shall best accomplish our present object by discussing the 
first principles of chemical philosophy, and illustrating them 
by a selection of facts, rather than by attempting the task of 
giving too much detail. 

183. State in which the elements exist. — At common 
temperatures, and when set free from combination, nearly 
all the elements are solids. Two, mercury and bromine, 
are fluids, and five are gases, namely, chlorine, fluorine, 
hydrogen, oxygen, and nitrogen. A few only of the 
elements are naturally found in a free or uncombined state, 
among which we may name oxygen, nitrogen, carbon, 
sulphur, and nine or ten metals. All the rest exist in 
combination with each other, and so completely concealed or 
disguised as to be known only to the chemist. 

182. How many elements do we know ? How are these usually 
divided ? How many are found as principal constituents of the 
globe? 183. In what state do the elements exist? Which are 
fluids ? Which are gases ? Which are free or uncombined ? In 
what state are the others ? 
12 



134 ELEMENTS AND THEIR LAWS OF COMBINATION. 



1. Combination by Weight. 

184. The laws by which the elements unite to form com- 
pounds, are included in the four following propositions. 

1st law. A compound of two or more elements is always 
formed by the union of certain definite and unalterable pro- 
portions of its constituent elements. 

This is the law of definite proportions. 

2d law. When two bodies unite in more proportions than 
one, these proportions bear some simple relation to each 
other. 

This is the law of multiple proportions. 

3d law. When a body (a) unites with other bodies, (b, c, 
d, &c.,) the proportions in which b, c, and d, unite with a, will 
represent in numbers the proportions in which they will unite 
among themselves, in case such union takes place. 

This is the law of equivalent proportions. 

4th law. The combining proportion of a compound body 
is the sum of the combining weights of its several elements. 

This is the law of the combining numbers of compounds. 

These four laws are the foundation of all chemical science, 
and should receive the attention which their great importance 
demands. We will briefly illustrate their meaning, which 
will be done, however, more effectually by the constant use 
we shall have to make of them, on almost every succeeding 
page of this treatise. 

185. Definite Proportions. — Analysis shows us that a 
given compound is always formed of certain elements in defi- 
nite proportions, and that no change can take place in the 
number or proportion of its constituent elements, without 
destroying its peculiar character, and forming a new sub- 
stance. Thus, in nine grains of water there are eight grains 
of oxygen and one grain of hydrogen. Any attempt to form 
water from any other proportion of its elements would be 
useless. Constancy of composition is essential to the being 
of chemical compounds. 

186. Multiple Proportions. — If a body (A) unites with a 
body (B) in more proportions than one, thus producing more 

184. State the first law of combination. What is this law called ? 
What is the second law ? What is this law called ? What is the 
third law, and what called ? The fourth, and what called ? What 
is said of these laws ? 183. What has analysis shown ? Illustrate 
this? 



COMBINATION BY WEIGHT. 135 

than one compound of the two elements, these proportions 
bear a simple relation to each other. (1.) We may have a 
series of compounds represented by A + B : A + 2B : A + 3B : 
A + 4B : A-f-5B : in which one, two, three, four, and five 
parts by weight of B, unite with one part of A, forming five 
separate and distinct compounds. Several examples of this 
law will be found in the following pages. (2.) In place of 
the simple ratio of numbers here explained, we may have 
another series of compound bodies, whose elements bear to 
each other an intermediate ratio. Thus the expressions, 
2A + 3B : 2A + 5B : 2A + 7B : represent a series of com- 
pounds, of which our future studies will afford us several 



187. Equivalent Proportions. — This may be considered 
as the most important law in chemical philosophy, and its 
discovery and application have been the great cause of the 
rapid advance of modern chemistry. Chemical analysis has 
shown that the body, oxygen, can form one definite com- 
pound, or more than one, with every other element yet dis- 
covered, except perhaps fluorine. The compounds of oxy- 
gen with the elements being perfectly definite, (183,) can 
all be expressed in numbers, which numbers will truly ex- 
press the combining weights of the several bodies. For the 
sake of illustration, let us assume that it requires eight parts 
by weight of oxygen to unite with each of the other elements, 
and that these eight parts require various weights of the 
several elements. We can then make a table which shall 
correctly express these numerical relations. 

6 parts of carbon. 

1 part of hydrogen. 

35-41 parts of chlorine. 

108-12 of silver. 

27-14 of iron. 

101-27 of mercury. 
_ 16-09 of sulphur. 

And we might go on thus through the whole list of ele- 
mentary substances, analyzing their several compounds with 
oxygen, and setting down the combining numbers of each 
in one table. The few examples given above are, however, 



186. Illustrate the law of multiple proportions. 187. Illustrate 
the law of equivalent proportions. What is said of oxygen ? "What 
is assumed for illustration ? How do other bodies staud related to 
oxygen ? How has this been determined ? 



Thus, 8 parts of oxygen unite with 



136 ELEMENTS AND THEIR LAWS OF COMBINATION. 

sufficient for our purpose. Oxygen is selected as the term 
of comparison for the other bodies, because it almost uni- 
versally unites with the several other elements. The number 
8 is attached to it, because hydrogen, which is made the unit 
in our books, enters into combination in a smaller proportion 
than any other body. We might with equal propriety make 
oxygen unity, when hydrogen would be expressed by a 
fractional number. But taking oxygen as 8, all the other 
numbers expressing the combining weight of each element 
have been determined with great care, by often repeated 
analyses. Let it be understood, then, that if any of the 
bodies in the table should form compounds with each other, 
the weights in which they will unite will be in the exact pro- 
portion of the numbers severally affixed to them. Thus, if 
hydrogen unites with chlorine to form a new compound, 
(hydro-chloric acid,) it will require one part of hydrogen to 
35*41 parts of chlorine to form such compound. One pound 
of hydrogen will unite to 35*41 pounds of chlorine, and will 
form 36-41 pounds of the compound. Any excess or de- 
ficiency of either of the elements will make no difference 
with the result, and the above law will in all cases be found 
strictly true. If sulphur and mercury unite to form a third 
body, it will be only in the proportion of the numbers 16-09 
and 101*26 ; and if sulphur unite with iron, it will be as 
16*09 : 27*14. 

We see then that the several numbers are truly the 
equivalents of each other, as they are all the equivalent of 
oxygen, and are, therefore, most appropriately called equiva 
lent proportions, or equivalent numbers. 

188. Table of Chemical Equivalents. — In the following 
table, the equivalent or combining numbers of all the ele- 
mentary bodies are given in accordance with the latest and 
best authorities. Two columns of combining proportions are 
given ; in the first, hydrogen, and in the second, oxygen, is 
used as the unit of comparison. Because hydrogen enters 
into combination with other bodies in a smaller weight than 
any other known element, it has generally been used in 
Great Britain and in this country as the basis of the scale of 



Illustrate this in the case of hydro-chloric acid. If there is an 
excess or deficiency of either element, what then ? What term is 
most appropriate to express this ? 188. What does the table show 
us ? What is said of the hydrogen scale, and why has it been used f 



COMBINATION BY WEIGHT. 



137 



equivalent numbers. It was also believed, and is still, by 
some good chemists, that the numbers expressing the com- 
bining weights of all bodies would be found, on more accurate 
research, to be simple multiples of the unit of hydrogen. If 
this view were correct, it would give us the great convenience 
of avoiding fractional numbers. But the most rigid experi- 
ments have failed to prove this idea to be true, and as it has 
no necessary foundation in the nature of things, we are not 
at liberty to adopt it. Berzelius, and most European chemists, 
assume oxygen as 100; and the second column of figures 
in the table gives the equivalents according to this scale. 



TABLE OF 


ELEMENTARY 


SUBSTANCES, WITH THEIR EQUIVALENTS AND 






SYMBOLS. 










H=l, 








H=l, 






Sym- 


or 






Sym- 


or 






bol.* 


Oxy.=8 


Oxy.= 100 




bol. 


Oxy.=8 


Oxy.=100 


Aluminium, 


Al 


1369 


171.17 


Manganese, 


Mn 


27-67 


345-89 


Antimony, 


Sb(l) 


129 04 


1612 90 


Mercury, 


Hg(6) 


101-26 


126582 


Arsenic, 


As 


7521 


94008 


Molybdenum, 


Mo 


47-88 


598.52 


Barium, 


Ba 


6855 


856-88 


Nickel, 


Ni 


2950 


36968 


Bismuth, 


Bi 


7095 


886-97 


Nitrogen, 


N 


1406 


175.75 


Boron, 


B 


10-90 


13620 


Osmium, 


03 


99-56 


124449 


Bromine, 


Br 


78 26 


97831 


Oxygen, 


O 


8- 


100- 


Cadmium, 


Cd 


55-74 


696-77 


Palladium, 


Pd 


5327 


665 90 


Calcium, 


Ca 


20- 


250- 


Phosphorus, 


P 


3138 


39228 


Carbon, 


C 


6- 


75- 


Platinum, 


PI 


98 68 


123350 


Cerium, 


Ce 


» 4598 


574.70 


Potassium, 


K(7) 


39- 19 


489-92 


Chlorine, 


CI 


3541 


44265 


Rhodium, 


R 


52 11 


65139 


Chromium, 


Cr 


2814 


35182 


Selenium, 


Se 


3957 


494-58 


Cobalt, 


Co 


29 52 


368-99 


Silicon, 


Si 


22 18 


27731 


Columbium, 


Cm 


184 59 


230743 


Silver, 


Ag (8) 


108- 12 


135161 


Copper, 


Cu(2) 


3165 


395 70 


Sodium.. 


Na (9) 


2327 


290 90 


Didymium, 


Di 






Strontium, 


Sr 


4:5-78 


54729 


Fluorine, 


F 


18-70 


233-80 


Su!phur,*»>-~ 


S 


1609 


201.17 


Glucinum, 


G 


2650 


331-26 


Tellurium, 


Te 


64.14 


601-76 


Gold, 


Au(3) 


99.44 


1243 


Thorium, 


Th 


5959 


744 90 


Hydrogen, 


H 


1- 


12-5 


Tin, 


Sn(10) 


5882 


735 29 


Iodine, 


I 


126-36 


1579-50 


Titanium, 


Ti 


24 29 


303 69 


Iridium, 


Ir 


98 6S 


1233 50 


Tungsten, 


W(ll) 


94 64 


1183 


Iron, 


Fe(4) 


2714 


33921 


Vanadium, 


V 


6855 


656 89 


Lantanum. 


Ln 






Uranium, 


u 


60- 


750- 


Lead, 


Pb(5) 


10356 


1294-50 


Yttrium, 


Y 


3220 


402.51 


Lithium, 


L 


6-43 


80 33 


Zinc, 


Zn 


33 00 


412 50 


Magnesium, 


Mg 


1267 


15835 


Zirconium, 


Zr 


33 62 


42020 



*In the symbols, the Latin names of the elements are employed. 
Eleven of these are not in common use, viz : (1.) Stibium, (2.) Cu- 
prum, (3.) Aurum, (4.) Ferrum, (5.) Plumbum, (6.) Hydrargyrum, 
(7.) Kalium, (8.) Argentum, (9.) Natrium, (10.) Stannum, (11.) 
Wolframium, (from the mineral, Wolfram.) Columbium is fre- 
quently represented by the symbol Ta, from Tantalum, a name by 
which the European chemists distinguish this metal. 
12* 



138 ELEMENTS AND THEIR LAWS OF COMBINATION. 

It is obvious that the numbers of the oxygen scale are just 
twelve and a half times as large as those in the hydrogen 
scale; consequently, dividing the oxygen equivalents by 12*5 
will give the hydrogen numbers, and multiplying the latter 
by the same sum will give us the oxygen numbers. 

189. Combining Numbers of Compounds. — It has been 
stated that the equivalent or combining proportion of a com- 
pound body is always the sum of the combining equivalents 
of its elements. Strict experiment has established this im- 
portant law, which will receive constant illustration as we go 
on ; at present, however, we must accept it as truth, and not 
anticipate, by attempting to give examples which cannot be 
well understood until we have become somewhat familiar 
with chemical language, symbolic illustration, and the laws 
of affinity. 

2. Combination by Volume. 

190. Gaseous bodies, whether elementary or compound, 
combine not only in accordance with the laws just explained, 
but also according to a peculiar law of their own, whereby 
certain volumes of each are required. The volumes in 
which gaseous bodies unite, are either 1 to 1, or 1 to 2, or 
1 to 3, &c. Thus water is formed of 2 volumes or measures 
of hydrogen, and 1 volume of oxygen. In combining, these 
three volumes are condensed into two. If we take oxygen, 
hydrogen, chlorine, and nitrogen, in the proportions by weight 
in which they combine, or measure the volumes they occupy 
as gases, a very obvious relation will be observed between 
them ; the volume of oxygen being exactly one half that of 
each of the others. 

Thus, 8 grains of oxygen occupy 23-3 cubic inches. 

1 grain of hydrogen, 46*7 

35*41 grains of chlorine, 46*2 

14*06 grains of nitrogen, 46*5 

How is one scale translated into the other ? [Note. If the learner 
can commit the table to memory with the hydrogen equivalents and 
symbols, it will be of great service to him hereafter.] 189. What 
is said of combining numbers of compounds ? 190. How else than 
by weight do the gases combine ? Illustrate this. What relation is 
seen between the equivalent weights and volumes of bodies ? Name 
some examples. 



COMBINATION BY VOLUME. 



139 



The same is true of compound gases, and also all bodies 
which can be raised in vapor, as sulphur, iodine, and 
mercury. Solids, which combine with gases, are subject to 
the same law. Sulphur has -£ the volume of oxygen, and 
mercury 4 times. 

191. We can state this truth in another form. If we call 
the weight of a volume of oxygen 1000, then an equal 
volume of hydrogen will weigh 0-0625, and these numbers 
will represent the relative specific gravity of the gases. But 
in water, two volumes of hydrogen unite with one of oxygen, 
and we must, therefore, double the above hydrogen number, 
2 X -0626 = 0-125. Now these numbers, 1000 and 0-125, 
are exactly the equivalent numbers on the oxygen scale, 
100- and 12*5, or making hydrogen unity, then we have 
100-0-r-12-5 = 8 ox., and 0-125^-12-5 = 1 hyd. This re- 
lation between the specific gravity of gaseous bodies and 
their combining number, or chemical equivalents, is uni- 
versally true, and we might give a long table including these 
relations; but the following examples will answer: 



Gases and vapors. 


Specil 
Air=l. 


ic Gravities. 


Chemical Equivalents. 


Hydrogen=l. 


By volume. 


By weight. 


Hydrogen, 


0-069 


1- 


100 or 1 


1- 


Nitrogen, 


0-972 


14-03 


100 or 1 


14-06 


Oxygen, 


1-111 


16- 


50 or A 


8- 


Chlorine, 


2-470 


35-64 


100 or 1 


35-41 


Iodine vapor, 


8-701 


126-30 


100 or 1 


126-36 


Bromine vapor, 


5-393 


78- 


100 or 1 


78-26 


Mercury vapor, 


6-969 


101. 


200 or 2 


101-27 


Sulphur vapor, 


6-648 


96-54 


16-66 or| 


16-09 



When the numbers m the second column are the same as 
the equivalents, (or with only a fractional difference,) then a 
volume represents an equivalent. The other numbers are 
multiples of the equivalent. Thus, 2x8= 16, the number 
for the density of oxygen, and sulphur 16 X 6 = 96, the 
density of sulphur vapor. 

192. Conclusions. — (1.) If we know the proportions by 
volume in which two gases combine, and also their specific 



What of compound gases and solids ? 191. State this truth in another 
form. Is this relation of density and combining numbers general? 
Name some of the examples in the table. 192. What conclusions 
are drawn from the previous statement? ? 1st? 2d? 3d? 4th? 



140 ELEMENTS AND THEIR. LAWS OF COMBINATION. 

gravities, we can calculate the composition of the compound 
by weight. (2.) Or we can foretell the density of a com- 
pound by knowing the volumes and specific gravities of its 
elements. (3.) If we know the volume and specific gravity 
of one of the two elements of a compound, and of the com- 
pound itself, we can then calculate its composition by weight. 
(4.) If we know the specific gravity and composition of a 
compound by weight, we can then calculate its composition 
by volume. Many examples will be found in elementary 
chemistry of the practical application of these rules. 

3. Chemical Nomenclature and Symbols. 

193. Names of the Elements. — Some of the elementary 
bodies have been known from the remotest antiquity, and 
were in common use long before the science of chemistry 
was heard of. Thus several metals, as Copper, (Cuprum,) 
Gold, (Aurum,) Iron, (Ferrum,) Mercury, (Hydrargyrum,) 
Silver, (Argentum,) Lead, (Plumbum,) Tin, (Stannum,) 
have long been known either by the names we now give 
them, or by those Latin terms of which our English names 
are translations. No descriptive meaning is conveyed by 
such terms as these, nor by such as Sulphur and Carbon, 
The alchemists named the metals after the various planets. 

Thus, Gold was called Sol, the Sun ; Silver, Luna, the 
Moon ; Iron, Mars ; Lead, Saturn ; Tin, Jupiter ; Quick- 
silver, Mercury ; and Copper, Venus. Hence formerly the 
astronomical signs or symbols of these planets were em- 
ployed by alchemists and mineralogists to represent the 
names of these metals, and they are still in use in some 
countries. 

Several of the elements have been named from some 
prominent or distinguishing physical property of color, taste, 
or smell, which they possess : thus Bromine is so called 
from the Greek word bromos, fetor ; Chlorine, from chloros, 
green, in allusion to its greenish color ; Chromium, from 
chroma, color, because it makes highly colored compounds, 
as chrome-yelloio ; Glucinum, from glukus, sweet, from the 
sweet taste of its salts ; Iodine, from ion, a violet, and eidos, 

193. Whence have some of the elements, as copper, &c, received 
their names? What did the alchemists call the metals ? On what 
other principles have some been named ? Give instances. 



CHEMICAL NOMENCLATURE AND SYMBOLS. 141 

in the likeness of; and so for many others. Another class 
of names has been contrived from what was supposed to be 
the characteristic attribute of the body in combination. Thus, 
Oxygen was so named because many of its compounds are 
acids, from the Greek, oxus, acid, and gennao, I produce. 
Hydrogen is from hudor, water, and gennao, I produce. We 
might thus go through the whole list, but it is unnecessary, 
as we shall have again to give the etymology of these words 
when we speak of each element. 

194. Names of Compounds. — All chemical compounds 
derive their names from one or more of their constituents, 
according to certain fixed and simple rules, which we must 
very briefly explain. When two elements unite, the 
compound is called binary, from bis, twice ; thus water, 
sulphuric acid, oxyd of silver, and oxyd of iron, are binary 
compounds. Compounds of binary combinations with each 
other, as of sulphuric acid with soda, forming sulphate of 
soda, or Glauber's salts, (and the salts, generally so called,) 
are called ternary compounds, (from ter, thrice.) Com- 
pounds of salts with each other, (as in the case of alum, 
which is a compound of sulphate of potash and sulphate of 
alumina,) are named quaternary compounds, from quatuor, 
four. 

195. All the compounds of oxygen with the other ele- 
ments are called either oxyds or acids. Thus, water in 
chemical language is the oxyd of hydrogen ; the chemical 
name of potash is the oxyd of potassium. It has been be- 
fore stated, that oxygen forms compounds with all the other 
elements, (187.) Some of these compounds have what we 
commonly call acid* properties : thus, the compounds of 
oxygen and sulphur are called acids, and not oxyds. Oxyds 
are divided into two classes ; (a) neutral oxyds, like water ; 



194. How are compounds named ? What are binary compounds ? 
What ternary? What quaternary? 195. What are the oxygen 
compounds called ? Give instances. How are oxyds described ? 
Notes: What are acids ? What alkalies ? What bases ? 



* Acids are known by their taste in some cases, and by their 
power of turning the vegetable blues to red; but more particularly 
by their power of uniting with and saturating alkalies and other 



142 ELEMENTS AND THEIR LAWS OF COMBINATION. 

(b) alkaline* oxyds and bases,f like potash, alumina. When 
the same element unites with oxygen in more than one pro- 
portion, (184, 2d,) forming two or more oxyds, then they 
are distinguished by the Greek prefix, proto, (protos, first,) 
applied to that body which has the least portion of oxygen, 
which is called the protoxyd ; deuto, (deuteros, second,) is 
prefixed to the next degree of oxidation, giving us the term 
deutoxyd ; trito, (tritos, third,) to the body containing still 
more oxygen than the deutoxyd. The oxyd which contains the 
largest dose of oxygen with which the body is known to unite, 
is also called the peroxyd, from the Latin, per, which is a par- 
ticle of intensity in that language. Thus there are two oxyds 
of hydrogen, the protoxyd (water) and the peroxyd ; there 
are three oxyds of manganese; (1.) the protoxyd, (2.) the 
deutoxyd, (3.) the peroxyd of manganese. Some oxyds are 
formed in the proportion of 2 to 3, or once and a half. Such 
oxyds are distinguished by the term sesquioxyds, from the 
numeral sesqui, (once and a half.) Certain inferior oxyds 
are called suboxyds. 

196. The binary compounds of chlorine, and some other 
elements which resemble oxygen in their manner of combi- 
nation, and in their relations to electrical decomposition, are 
also distinguished in the same manner as oxygen. Thus, 
with the other elementary bodies : 

Chlorine forms Chlorids. 
Bromine " Bromids. 
Iodine " Iodids. 
Fluorine " Fluorids. 
Oxygen " Oxyds. 

197. The binary compounds of sulphur analogous to the 
oxyds are called sulphurets, and not sulphids. The prefix 

Explain the terms expressing different degrees of oxydation, and 
their use. 1st, proto. 2d, deuto. 3d, trito. 4th, per. 5tk, sesqni. 
6th, stib. 196. How are the binary compounds of chlorine, &c, 
named ? Give instances. 

* Alkalies are soluble bodies, with a hot, acrid taste, which have 
the power of saturating acids, and of turning the reddened vegetable 
blues to blue or green. 

f Base is a term given to all oxyds which are not acids : it is a 
more general and comprehensive term than alkali. In fact, all 
bodies, simple and compound, are properly divided into bases and 
acids, or electro-positive and electro-negative bodies. 



CHEMICAL NOMENCLATURE AND SYMBOLS. 14-3 

hi (double) is more commonly used before the compounds of 
chlorine, sulphur, &c, than deuto, which is used before the 
oxyds. Thus, it is more usual to say bichloride of carbon, 
and bisulphuret of iron, than deutochloride of carbon, and 
deutosulphuret of iron. When the name of the element to 
which this prefix is made begins with a vowel, the consonant 
n is introduced as making a more euphonious word ; thus 
we say biniodid of lead, rather than bi-iodid of lead. Com- 
pounds of phosphorus and carbon with electro-positive ele- 
ments, are distinguished by the termination uret, like those 
of sulphur; thus, we say the sulphuret of carbon, carburet 
of iron, and phosphuret of lead. In all such cases, the 
name of the element which most resembles oxygen, (i. e. the 
electro-negative element,) is that which stands first in the 
name of these compounds, and which has the termination 
affixed to it. Thus, one of the compounds of chlorine and 
phosphorus is called chlorid of phosphorus, and not phos- 
phuret of chlorine ; sulphuret of carbon, and not carburet 
of sulphur. 

198. The acid compounds of oxygen are named from the 
substance in combination with the oxygen, with the addition 
of the termination ic, the word acid being always appended. 
Thus, one of the compounds of nitrogen and oxygen is 
termed nitric acid ; of chromium and oxygen, chromic acid. 

If two acid compounds of oxygen are formed with an ele- 
ment, the termination ous is applied to that which has the 
least oxygen ; thus we have sulphurous acid, and sulphuric 
acid, as the names for two very dissimilar acids of sulphur. 

Sometimes a compound has been discovered containing 
less oxygen than that compound which has already received 
the termination ous ; then the term hypo is prefixed, (from 
the Greek hupo, under,) and we then have the term hypo- 
sulphurous ; or hyposulphuric, provided an intermediate 
compound is formed between the sulphurous and sulphuric 
acid. On the same plan, we say hyperchloric acid, (from 
huper, above,) to distinguish the acid of chlorine having a 
higher proportion of oxygen than chloric acid, before named ; 
perchloric acid has the same meaning, and may be used 



197. How is the term hi used ? In the names of sulphur, iodine, &c, 
which element stands first ? 198. How are the acid compounds of 
oxygen named ? Explain the use of the terminations " ic" and 
" 02«." How is hypo used in this connection, and how hyper? 



144 ELEMENTS AND THEIR LAWS OF COMBINATION. 

with equal propriety. All other analogous acids are named 
on precisely the above principles. 

199. Sulphur acids and hydrogen acids are those where 
sulphur and hydrogen take the place of oxygen. Thus, 
sulpharsenic-acid is an acid compound of arsenic and sul- 
phur. Hydrochloric acid is the acid formed from the union 
of hydrogen and chlorine.* In the same way, we have 
hydrobromic, hydrofluoric, and hydriodic acids, as acids of 
bromine, fluorine, and iodine. 

200. (2.) Ternary compounds, or salts, are named from 
the acid which they contain ; the termination ic being 
changed into ate, and ous into ite. Thus, the salt formed 
from the union of soda and nitric acid is called the nitrate 
of soda, and that formed with nitrous acid is called the 
nitrite of soda; the salts of hyponitrous acid are called 
hyponitrites, and of hyperchloric acid, hyperchlorates, &c. 
The species is always indicated by the oxyd ; thus, the 
nitrate of lead is the same as the nitrate of the oxyd of lead, 
and nitrate of soda is the same as nitrate of the oxyd of 
sodium ; the word oxyd being understood, is generally 
omitted. A bisulphate has twice, and a sesquisulphate once 
and a half as much acid as a sulphate. The excess of base 
in subsalts is sometimes expressed by the Greek prefix di, 
twice ; thus, the dichromate of lead has twice as much of 
the base lead as the chromate of lead. 

201. (3.) Quaternary Compounds. — The double salts are 
named from their bases ; thus alum, which is formed of sul- 
phate of alumina and sulphate of potash, is called double 
sulphate of alumina and potash. The chlorid of potassium 
and platinum is another double salt, formed from the union 
of a chlorid of platinum and chlorid of potassium. 

202. The chemical nomenclature, when once understood, 
enables us after a little use to form, in most cases, from the 
mere name of the compound substance, a correct idea of its 



199. Sulphur acids and hydrogen acids are how named ? 200. 
How are salts named ? Give examples. How are the species named ? 
What is a bi and sesqui sulphate ? What meaning has the prefix di ? 
201. (3.) How are double salts named ? Give examples. 



* In strict uniformity to rule, the term chlorohydric is correct, but 
use has established the other. The same remark is true of bromo- 
nydric, fluohydric, and iodohydric acids. 



CHEMICAL NOMENCLATURE AND SYMBOLS. 14-5 

composition, and of the proportions of its constituents. This 
great advantage is possessed by no other science, and cannot 
be too highly estimated. There are a good many compounds, 
however, that have been discovered of late years, for which 
this nomenclature provides no names. But we have certain 
written expressions, by means of which we can convey an 
idea of all chemical compounds with a mathematical precision 
and great convenience. 

203. Chemical Symbols of the Elements. — In the table 
of Elementary Bodies (168) the " symbols" of the several 
elements will be found opposite to their names. The sym- 
bols are merely the first letter of each name, or the first two, 
when more than one element begins with the same letter ; 
thus O stands for oxygen, and Os for Osmium ; P stands for 
Phosphorus ; PI for Platinum, and Pd for Palladium. The 
second letter in all such cases is small, a capital letter being 
uniformly used for the first. The Latin names are invariably 
used for the abbreviation, and for this reason there are eleven 
symbols, unlike the common names of the elements they 
represent. (See note to 188.) Prof. Berzelius contrived 
the system of symbols now in use, and by a happy thought 
he made each symbol represent not merely the svbstance for 
which it stands, but one equivalent of each substance. Thus 
O stands not for oxygen in general, but for one equivalent of 
that element; or, hydrogen being unity, for the number 8. O 
and 8 are therefore interchangeable expressions, while O 2 , 
O 3 , &c, represent 2x8 and 3x 8, or 16 and 24, according 
to the second law of chemical combination, (184.) 

Compounds are represented by using merely the symbols, 
and sometimes uniting them by the sign of addition, ( + •) 
Thus water will be represented by HO or H-f-O, which 
means one equivalent of each element, 1+8 = 9, which is 
the combining number of water. Protoxyd of lead is thus 
written PbO, or Pb + O. 

204. When more than one equivalent of an clement is in 
combination, we then prefix a number expressing i:, like an 
algebraic co-efficient, (as 50,) or the number may be applied 



202. What great advantage has the chemical nomenclature ? 
203. What are chemical symbols ? Give examples. What names 
are abbreviated ? Whose contrivance are the symbols ? For what 
does the symbol stand? Illustrate. How are compounds repre- 
sented ? Give examples on the black-board. 
13 



146 ELEMENTS AND THEIR LAWS OF COMBINATION. 

above on the right, (as O 5 ,) or below on the right, (as 5 ;) 
each of these expressions means five equivalents of oxygen. 

We can write nitric acid N50, or NO 5 , or N0 5 , the latter 
being the usual mode ; sometimes, but not often, the + or 
comma (,) is used between them, as N + 5 , or N,0 5 . 
Such expressions are called formula ; thus the formula for 
sulphuric acid is S0 3 , or S + 3 , from which we know that 
the combining number of sulphuric acid is 16 + 8 3 , or 
16 + 24 = 40. When two compounds unite to form a new 
body, the sign -f-, or (,) is used between them; thus, sul- 
phate of oxyd of iron is written FeO + SO 3 , or FeO,S0 3 . 
The small figures apply only to the letters to which they are 
attached ; larger figures used before the compound, apply to 
the whole formula ; thus, 3S0 3 means three equivalents of 
sulphuric acid ; but the sign + prevents the passage of this 
meaning beyond the sign. Thus 2FeO-fS0 3 means two 
equivalents of oxyd of iron and one of sulphuric acid ; in 
order to make the figures apply to both, we must write it 
2(FeO + S0 3 ,) or 2(FeO,S0 3 .) 

In chemical symbols, the oxygen, or element most nearly 
resembling it, (i. e. the electro-negative element,) is placed 
last ; the base (or electro-positive element) being placed first. 
Thus we say S0 3 for dry sulphuric acid, and not 3 S. A com- 
pound of sulphuric acid (S0 3 ) and water contains 2 equiva- 
lents of water, only one of which is however chemically 
combined as a base with the acid. We can make this 
apparent to the reader in constructing the formula thus, 
HO,S0 3 -fHO; the comma signifies a closer union than 
the +, and the first equivalent of water is in intimate union 
with the acid, forming a sulphate of water, while the second 
portion is combined with this sulphate. Compounds which 
contain water, like common sulphuric acid, nitric acid, and 
many mineral bodies, are termed hydrous. 

205. The symbols are sometimes abbreviated still further, 
to simplify the expression of very complex combinations. 
This is done by expressing one equivalent of oxygen by a 



204. How is more than one equivalent expressed ? Show the 
different modes in which nitric acid is expressed ? How is the 
union of compqunds expressed ? Tell the difference between the 
small and large figures. Which element is placed first in symbols ? 
Illustrate. How can we make the peculiar construction of hydrous 
sulphuric acid seen ? What are hydrous bodies ? 



CHEMICAL AFFINITY. 14-7 

dot, two by two dots, &c. Thus S signifies the same as S0 3 , 
(dry sulphuric acid.) Common crystallized alum is written 
in full, thus, 

A1A,3S0 3 + KO,S0 3 + 24HO. 
We can conveniently condense this long expression ; thus 

AlS 3 + KS-f24H. 

The short line under the Al signifies two equivalents of the 

base. Sometimes the double equivalent of base is denoted 

by a black letter, thus, Al, in place of the line beneath. In 
Berzelius's original symbols the short line is made through 
the type in the lower half. Sulphur is in like manner signi- 
fied by a comma ; thus, bisulphuret of iron, Fe,S 2 , may be 

more shortly written Fe. The constant use of these sym- 
bolic expressions in the elementary chemistry will soon 
familiarize the learner with their use and meaning. They 
have contributed very much to the progress of the science, 
and are invaluable as a ready means of comparing as well 
as expressing the composition of compound bodies. 

4. Chemical Affinity. 

206. We have already explained (12 and 13) what is 
meant by chemical affinity, as the power which unites two 
or more unlike bodies to form a third substance, whose 
properties differ from those of its constituents. Chemical 
affinity, or the capability of union, is not possessed alike by 
all bodies. Oxygen, as before stated, is the only element 
capable of forming chemical compounds with all other ele- 
ments. Carbon can unite with oxygen, sulphur, hydrogen, 
and some other bodies, but no compound has been formed 
between it and gold, silver, fluorine, aluminium, iodine, bro- 
mine, &c. It is, therefore, said to have no affinity for these 
bodies, or no capability of union with them. The power of 
union among bodies, or affinity, is exceedingly different in 
degree, and is much affected by many circumstances. Thus 



205. Illustrate on the black-board the abbreviation of symbols in 
the case of alum. How is sulphur in combination signified by- 
symbols ? 206. What is chemical affinity ? Is it equal in ail 
bodies ? Illustrate by examples. 



148 ELEMENTS AND THEIR LAWS OF COMBINATION. 

a body A may unite with a body B, forming a third body 
AB ; but if a body C had been present, A might have so 
much more affinity for C than it has for B, as to unite with 
it, forming AC, while B would remain unaffected. For 
example, sulphuric acid and soda will unite to form Glau- 
ber's salts, or sulphate of soda ; but if soda and baryta had 
both been " present, and sulphuric acid were added, only the 
sulphate of baryta (or heavy spar) would be formed, and 
the soda would remain disengaged, unless there was sulphuric 
acid enough to satisfy all the baryta and soda too. This is 
what is sometimes called elective affinity, as if the acid 
selected the baryta rather than the soda. 

207. The more unlike, as a general thing, any two bodies 
are in chemical properties, the stronger is their disposition to 
unite. The metals, as a class, have very little disposition to 
unite with each other, and when they do so it is not generally 
in chemical proportions. But they do unite vviih oxygen, 
chlorine, sulphur, &c, forming fixed and determinate com- 
pounds. The alkalies, potash and soda, form no proper 
compound with each other, and their alkaline properties are 
not altered by such union. Sulphuric and nitric acid may 
be mingled in any proportion, but no new compound is 
formed, and the mixture is still acid. But if the potash and 
soda be put with the nitric and sulphuric acid, separately, 
and in their combining proportions, the result will be two 
compound bodies, having neither acid nor alkaline properties. 
If the nitric acid is added to its equivalent of potash, we shall 
have saltpetre, or nitrate of potassa, while the sulphuric acid 
in like manner will unite with its equivalent of soda, forming 
sulphate of soda, or Glauber's salts. 

208. Solution is the result of a feeble affinity, but one in 
which the properties of the dissolved body are unaltered ; 
thus, sugar is dissolved in all proportions in water or alcohol, 
and a drop of the solution may be mingled in an ocean of 
water. Camphor is soluble in alcohol, in any proportion, 
but the addition of water to the solution will cause the cam- 
phor to be thrown down. Gum is soluble in water, but not 
in alcohol. We have already seen, that the solution of 



What is meant by "elective affinity"? 207. What principal 
condition of affinity is named ? Illustrate this. 208. What is said 
of solution ? 



CHEMICAL AFFINITY. 149 

various salts in water would produce cold (111) from the 
change of state in the body dissolved. 

209. The circumstances which modify the action of 
affinity are numerous, some of which we may briefly notice. 
We have said (16) that chemical affinity existed only among 
unlike particles, and at insensible distances. Intimate con- 
tact among particles is, therefore, in the highest degree 
necessary to promote chemical union. Any circumstance 
which favors such contact will increase the activity of, or 
disposition to, chemical combination. Solution brings par- 
ticles near together, and leaves them free to move among 
each other ; substances in a state of solution have, therefore, 
an opportunity to unite, which they do not possess when 
solid. Hence the old maxim, " Corpora non agunt nisi sint 
soluta." Carbonate of soda and tartaric acid, for example, 
both in a dry state, will never unite ; but the addition of water 
will at once, by dissolving them, bring about a union. Heat 
will often cause union to take place, being, in fact, a most 
powerful means of solution. Sand or silica will not unite 
with soda or potash by contact or aqueous solution, but if 
the mixture in proper proportions is strongly heated, union 
takes place and glass is formed. Sulphur will not unite with 
cold iron, but if the iron be heated to redness, or the sulphur 
melted, a vigorous union takes place, and a sulphuret of iron 
results. 

Cohesion (10) is strongly opposed to chemical union, or 
affinity, and any means which will overcome it will promote 
the union of the elements. Solution and heat both act by 
overcoming cohesion ; and the fine mechanical division of a 
body, or pulverization, does the same. 

210. Bodies in the nascent* state (as it is called) will 
often unite, when under ordinary circumstances no affinity is 
seen between them. Thus hydrogen and nitrogen gases, 
under ordinary circumstances, do not unite if mingled in the 
same vessel ; but when these two gases are set free at the 
same time, from the decomposition of some organic matter, 

209. What circumstances modify or are essential to affinity ? How 
does solution favor it ? Illustrate. How does heat favor it ? Illus- 
trate. How does cohesion affect it ? What counteracts cohesion ? 
210. What of bodies in the nascent state ? Illustrate this. 

* From nascent, being born, or in the moment of formation. 
13* 



150 ELEMENTS AND THEIR LAWS OF COMBINATION. 

they readily unite, forming ammonia. The- same is true of 
carbon under the same circumstances," which will then unite 
in a great variety of proportions with hydrogen and nitrogen, 
although no such union can be effected among these bodies 
separately. 

211. The quantity of matter, as well as the order and 
condition in which substances may be presented to each 
other, often exerts an important influence on the power of 
affinity. Thus vapor of water, when passed through a gun- 
barrel heated to redness, will be decomposed, the oxygen 
uniting with the iron, while the hydrogen escapes at the other 
end of the tube. On the contrary, if hydrogen gas is passed 
over oxyd of iron in a tube heated to redness, the oxygen of the 
oxyd unites with the hydrogen, leaving metallic iron, while 
steam (formed from the union of the hydrogen with the 
oxygen from the iron) issues from the open end of the tube. 
Numerous examples of this sort might be given, where the 
play of affinities seems to be determined by the preponderance 
of one sort of matter over another, or by the peculiar con- 
dition of the resulting compounds, as regards insolubility, or 
the power of vaporization. 

212. The presence of a third body often causes a union, 
or the exertion of the force of affinity, when this third body 
takes no part in the changes which happen. Thus, oxygen 
and hydrogen gases may be mingled without any combination 
taking place between them, although a strong affinity exists. 
If, however, a portion of platinum in a state of very fine 
division (spongy platinum) be introduced into the mixture, 
union takes place, sometimes slowly, but more often with an 
explosion, the platinum being at the same time heated to 
redness from the rapid union of the gases which takes place 
ill its pores. Advantage is taken of this fact in constructing 
the common instrument for lighting tapers by a stream of 
hydrogen falling on spongy platinum. No change is suffered 
in this case by the platinum, which seems to act by its 
presence only. Berzelius has proposed the term catalysis, 
from the Greek Tcata, by, and luo, to loosen, to express the 
peculiar power which some bodies possess of aiding chemical 
changes by their presence merely. We shall have occasion 

211. What of quantity of matter? Give an example. 212. What 
is meant by the influence of presence? Illustrate this. What other 
term expresses these cases ? 



ATOMIC THEORY. 151 

to refer to this subject again. The case of the platinum is 
much more intelligible than many other instances of con- 
tact-union and decomposition of which chemistry offers ex- 
amples, since it appears to act by its power of condensation, 
to bring the particles within combining distance. 

5. Atomic Theory. 

213. We have already (7 and 8) said something of atoms 
as being the smallest conceivable state in which matter exists. 
As all ponderable matter is assumed to be formed by an 
aggregation of a series of these atoms, the interesting question 
at once arises, do the chemical equivalents or combining 
weights of the several elements express the relative weights 
of their atoms? Dr. Dalton first proposed the view now 
universally accepted, which assumes this to be the fact. All 
that has been said in this chapter on the combining weights 
of bodies, &c, has been the result of rigorous chemical in- 
vestigation, and is capable of demonstrable proof. Dalton's 
hypothesis of the relative weights of ultimate atoms is only 
theoretical, but has been found to conform in a remarkable 
degree to the results of experience. We may feel some good 
degree of certainty in the belief that we know the actual re- 
lation of weight between the ultimate atoms or molecules of 
the elements. There is no doubt that the atom of sulphur is 
two times heavier than that of oxygen ; but we know nothing 
of their actual weight. 

214. We can now, perhaps, better understand why the 
equivalent numbers of bodies should always be multiples of 
each other. If the atom of oxygen be represented by eight, 
(and we cannot conceive of an atom as being divided,) then 
any compound containing more than one atom of oxygen, 
must have twice, thrice, or four times eight, and so on. On 
this view of atoms, all the four great laws of chemical com- 
bination (184) receive a remarkable corroboration, as a little 
reflection will show. The atomic weight of a body is there- 
fore as correct an expression as its equivalent weight, or 
combining proportion. We might easily illustrate this theory 
to the senses in a gross way, by a series of spheres so 
marked as to represent the several atoms of elementary 

213. What is the atomic theory? 214. What help does it give in 
understanding chemical facts ? 



1 52 CRYSTALLIZATION. 

bodies, the union of which would show the compound re- 
sulting from the union of atoms. 

6. Specific Heat of Atoms. 

215. Specific heat has already been explained, (106.) 
If in place of comparing equal weights of different bodies 
together, we take them in atomic proportions, we shall find 
the numbers representing the specific heat of lead, tin, zinc, 
copper, nickel, iron, platinum, sulphur, and mercury, to be 
identical ; while tellurium, arsenic, silver, and gold, although 
equal to each other, will be twice that of the nine previous 
bodies, and iodine and phosphorus will be four times as 
much. The general conclusion drawn from these and other 
similar facts is, that the atoms of all simple substances have 
the same capacity for heat. The specific heat of a body would 
thus afford the means of fixing its atomic weight. There 
can be no doubt of the truth of this in numerous cases, but 
experiments are still wanting to show it to be universally 
true. Compound atoms have in some cases been shown to 
have the same relations to heat as the simple. This is true 
of many of the carbonates, and some sulphates. A more 
minute discussion of the atomic theory would be out of place 
in this work. 

II. CRYSTALLIZATION. 

1. Nature of Crystallization and Primary Forms of 
Crystals. 

216. Nature of Crystallization. — The forms of living 
nature, both animal and vegetable, are determined by the 
laws of vitality, and are generally bounded by curved lines 
and surfaces. Inorganic or lifeless matter is fashioned by a 
different law. Geometrical forms, bounded by straight lines 
and plane surfaces, take the place in the mineral kingdom 
which the more complex results of the vital force occupy in 
the animal and vegetable world. The power which de- 
termines the forms of inorganic matter is called crystallization. 



215. What relation has specific heat to the atomic theory ? 216. 
What parallel is drawn between the forces of living and inorganic 
nature. 



NATURE OF CRYSTALLIZATION. 153 

A crystal is any inorganic solid, bounded by plane surfaces 
symmetrically arranged, and possessing a homogeneous 
structure. 

Crystallization is, then, to the inorganic world, what the 
power of vitality is to the organic ; and viewed in this, its 
proper light, the science of crystallography rises from the low 
station of being only a branch of solid geometry, to occupy 
an exalted philosophical position. We see, therefore, the 
importance of devoting a brief space to this subject in con- 
sidering the general principles of Chemical Philosophy. 

The cohesive force in solids (10) is only an exertion of 
crystalline forces, and in this sense no difference can be 
established between solidification and crystallization. The 
forms of matter resulting from solidification may not always 
be regular, but the power which binds together the molecules 
is that of crystallization. 

217. Circumstances influencing Crystallization. — Solu- 
tion is one of the most important conditions necessary to 
crystallization. Most salts and other bodies are more soluble 
in hot than in cold water. A saturated hot solution will 
usually deposit crystals on cooling. Common alum and 
Glauber's salts are examples of this. Solution by heat or 
fusion also allows of crystallization, as is seen in the crys- 
talline fracture of zinc and antimony. Sulphur crystallizes 
beautifully on cooling from fusion, and so do bismuth and 
some other substances. The slags of iron furnaces and 
scoriae of volcanic districts present numerous examples of 
minerals finely crystallized by fire. The glass, which cools 
slowly after long fusion, in the clay fire-pots of our glass- 
houses, has often beautiful star-formed opaque white crystals 
found in it, and the whole mass of the glass sometimes 
becomes crystalline and opaque. Blows and long continued 
vibration produce a change of molecular arrangement in 
masses of solid iron and other bodies, resulting often in the 
formation of broad crystalline plates. Rail-road axles are 
thus frequently rendered unsafe. In short, any change which 
can disturb the equilibrium of the particles, and permits any 
freedom of motion among them, favors the re-action of the 
polar or axial forces, (218,) and promotes crystallization. 



What is crystallization said to be ? What is the cohesive force ? 
217. Name some circumstances which influence crystallization. 



154 



CRYSTALLIZATION. 




Magnetism influences and promotes crystallization. When 
nitrate of mercury on a glass plate is 
placed over the poles of an electro- 
magnet, as in the figure, crystalliza- 
tion takes place in the curved lines 
here shown. By substituting a plate 
of copper for the glass, it is curiously 
etched in the magnetic curves by the 
acid of the silver salt. These experi- 
ments may be much varied by the ingenuity of the learner. 
The observations of Mr. R. Hunt have given us much new 
information on this point. 

218. Polarity of Molecules. — The laws of crystallization 
show that the molecules (or ultimate particles of matter) have 
polarity. That is, these molecules have three imaginary 
axes passing through them, whose terminations, or poles, are 
the centre of the attractions (10) by which a series of similar 
particles are attracted to each other to form a regular solid. 
These molecules are either spheres (a) or ellipsoids, (c,) and 
the three axes (N. S.) are always either the fundamental 
axes or the diameters of these particles. In the sphere (a) 



y/fl 


N^>C 


/si 

\NL_... 


s~ 


s\ 




/vi 


ix> 




/ i 


s 


W j 


y 




jp 


V 



these axes are always of equal length, and at right angles to 
each other, and the forms which can result from the aggre- 
gation of such spherical particles can be only symmetrical 
solids, such as the cube and its allied forms. The cube 
drawn about the sphere a may be supposed to be made up of 
a great number of little spheres (b) whose similar poles 
unite N. and S. In the ellipsoid (c) all the axes may vary 
in length, giving origin to a vast diversity of forms. All 



What is said of the power of magnetism in this respect ? 218. 
What do the laws of crystallization show ? What are the axes of 
molecules ? What forms have the molecules of bodies ? What 
forms can come from the spherical particles ? How may the struc- 
ture of the cube be shown ? How are the axes of the ellipsoid ? 



PRIMARY FORMS OF CRYSTALS. 



155 



matter not subject to the vital force is endowed with such 
polarity inherent in its molecules.* 

/ 219. Crystalline Forms. — The mineral kingdom presents 
us with the most splendid examples of crystals ; yet, in the 
laboratory we can imitate the productions of nature, and in 
many cases produce beautiful forms from the crystallization 
of various salts, which have never been observed in nature. 
The learner who is ignorant of the simple laws of crystal- 
lography, sees in a cabinet of crystals an unending variety 
and complexity of form, which at first would seem to baffle 
all attempts at system or simplicity. Numerous as the natu- 
ral forms of crystals are, however, they may be all reduced 
to six classes, comprising only thirteen or fourteen forms, 
which are called the primary forms, because all other crys- 
talline solids, however complex or varied, may be formed 
from them by certain simple laws. 

220. Primary forms. — The first class of primary forms 
includes the cube, (1,) the octahedron, (2,) and the dodeca- 
hedron, (3.) The 
faces of the cube 
are equal squares. 
The eight solid an- 
gles are similar, 
and also the twelve 
edges. The three 12 3 

axes are equal, (aa, bb, cc,) and connect the centres of 
opposite faces. The regular octahedron (2) consists of two 
equal four-sidecl pyramids, placed base to base. The six 
solid angles are equal, and so also the edges, which, as in 
the cube, are twelve in number. The plane angles are 60°, 
and the interfacial 109° 28' 16". The axes connect the 
opposite angles ; they are equal, and intersect at right angles. 



/■ 




z 


yS 


I...- 

4 




^e 


_.» 




1 


>" 




To what matter do these axial attractions belong ? 219. How 
are the complex forms of crystals arranged and simplified ? 220. 
Describe the first class of primary forms. 



* We thus see that atoms or molecules are, as before remarked, 
only the centres of several forces, whose aggregate results we call 
matter. Under the influence of heat, the crystallogenic attraction 
loses its polarity and force, and the body becomes liquid or gaseous. 
The return to a solid state can occur again only when the attractions 
become polar or axial. 



156 



CRYSTALLIZATION. 



This class is also called the monometric, (monos, one, and 

metron, measure,) the axes being equal. 

221. The second class includes the square prism, (4,) and 

square octahedron, (5.) In the square prism (4) the eight 
solid angles are right angles, and 
similar, as in the cube. The eight 
basal edges are similar, but differ 
from the four lateral. The two 



y 




a 


y 


i 




c 


i 




cS 






y 






y 


s 


& 


y 




basal faces are squares, the four 
lateral are parallelograms. The 
axes connect the centres of oppo- 
4 5 site faces, and intersect at right 

angles. Square prisms vary in the length of the vertical 
axis, (a, a,) which is hence called the varying axis ; the 
lateral axes (bb> cc) are equal. This class is also called the 
dimetric, (dis, twofold, and metron, measure.) 

222. The third class contains the rhombic prism, (6,) the 
rectangular prism, (7,) and the rhombic octahedron, (8.) 

The rhombic prism (6) 
has two sorts of edges, 
two acute and two ob- 
tuse. The solid angles 
are, therefore, of two 
kinds, four obtuse and 
four acute. The axes 
6 7 8 are unequal, and cross 

at right angles. The lateral connect the centres of opposite 
edges, bb, cc. The basal faces are rhombic. The rect- 
angular prism (7) has all its solid angles similar. There 
are three kinds or sets of edges, four lateral, four longer 
basal, and four shorter basal. The axes connect the centres 
of opposite faces, and intersect at right angles. The three 
are unequal. The rhombic octahedron (8) has three unequal 
axes, connecting opposite solid angles. All the sections in 
this solid are rhombic. This class is also called the trimetric, 
from tris, threefold, and metron, measure. 

223. The fourth class contains the oblique rhombic prism, 
(9,) and the right rhomboidal prism, (10.) The oblique 
rhombic prism is represented in the figure as inclining away 






6 




221. What are the forms of the second class? Describe them. 
222. What forms make up the third class ? Describe them. 223. 
What forms does the fourth class contain ? How do they differ ? 



PRIMARY FORMS OF CRYSTALS. 



157 







10 



from the observer, the prism being in position when standing 
on its rhombic base. The upper and 
lower solid angles in front are dis- 
similar, one obtuse and the other e 
acute. The four lateral solid angles 
are similar. Two of the lateral 
edges are acute, and two obtuse ; and 
the same is true of the basal. The 
lateral axes are unequal ; they connect the centres of oppo- 
site lateral edges, and intersect at right angles. The vertical 
axis is oblique to one lateral axis, and perpendicular to the 
other. The right rhomboidal prism (10) has two obtuse 
and two acute lateral edges, and four longer and four shorter 
basal edges. The solid angles are of two kinds, four obtuse 
and four acute. The axes connect the centres of opposite 
faces ; one is oblique, the others cross at right angles. 
This is also called the monoclinate, (monos, one, and clino, 
to incline,) having one inclined axis. 

224. The fifth class includes the oblique rhomboidal 
prism. In this solid only those parts diagonally 
opposite are similar, and consequently it has six 
kinds of edges. The axes connect the centres 
of opposite faces. They are unequal, and all 
their intersections are oblique. This is called 
the triclinate class, from tris, three, and clino, 
to incline, the three axis all being obliquely in- 
clined. 

225. The sixth class includes the hexagonal prism, (12,) 
and the rhombohedron, 
(13 and 14.) The hex- f ^gft 
agonal prism has twelve 
similar angles, and the 
same number of similar 
basal edges. The lateral 
edges are six in number, 
and similar. The lateral 




!L. 




12 



13 




axes are equal, and cross at 60°, connecting the centres of 
opposite lateral faces or lateral edges. 



What other names have the first, second, and third classes ? 
224. What solid is included in the fifth class ? 225. Name the two 
solids in the sixth class of primary forms. How are the hexagonal 
7>rism and rhombohedron related ? 
14 



1 58 CRYSTALLIZATION. 

The rhombohedron is a solid whose six faces are all 
rhombs. The two diagonally opposite solid angles (a a) 
consist of three equal obtuse or equal acute plane angles, and 
the diagonal connecting these solid angles is called the verti- 
cal axis, (a a.) When the plane angles forming the vertical 
solid angles are obtuse, the rhombohedron is called an obtuse, 
(13,) and if acute, it is called an acute rhombohedron, (14.) 
The three lateral axes are equal, and intersect at angles of 
60° ; they connect the centres of opposite lateral edges. 
This will be seen on placing a rhombohedron in position and 
looking down upon it from above. The six lateral edges will 
be found to be arranged around the vertical axis, like the 
sides of a hexagonal prism. 

226. The mutual relations of the primary forms are well 
shown in the foregoing arrangement. Thus, in each of the 
six classes, the first named solid alone is, properly considered, 
a primary form, the others in each class being frequently 
found as secondaries to these. The six fundamental forms 
are the cube, square prism, right rectangular prism, oblique 
rhombic prism, or right rhomboidal prism, oblique rhomboi- 
dal prism, and the hexagonal prism, or rhombohedron. 

2. Cleavage. 

227. Common isinglass, or mica, will split into thin leaves 
or plates, which can be subdivided as long as our compara- 
tively clumsy instruments will allow. This property depends 
on the crystalline structure of the mineral, and is called its 
cleavage. Many other minerals possess the same property. 
Thus, galena (sulphuret of lead) can be broken only into 
cubes, or in directions parallel to one or more of the face&jof 
a cube. It differs from mica in having three cleavage di- 
rections, at right angles to each other. Fluor-spar, which is 
often found in cubes, can, by cleavage of the solid angles, be 
made into regular octahedrons. Calc-spar also admits of easy 
cleavage in three directions, but yields only rhombohedrons. 

Cleavage is not effected with equal ease in all minerals : 
in mica, this is produced by the finger-nail ; in others, a 



How are rhombohedrons distinguished ? 226. What is said of the 
relations of primary forms ? What six fundamental forms are named ? 
227. What is cleavage in minerals? On what does it depend ? Give 
examples. Is it equal in all minerals ? 



MEASUREMENT OF CRYSTALS. 



159 



slight blow in the direction of the cleavage is required, and 
some practice and skill are necessary to ensure success. — 
Quartz and several other minerals cleave only when heated 
and thrown into water ; other minerals do not cleave at all. 
Cleavage, when attainable, takes place parallel to some or all 
of the faces of the primary form. It is obtained with equal 
ease or difficulty parallel to similar primary faces, and with 
unequal ease or difficulty parallel to dissimilar primary faces ; 
and cleavage parallel to similar planes affords planes of 
similar lustre and appearance, and the converse. 



3. Measurement of Crystals. 

228. Common Goniometer* — The angles of crystals are 
measured by means of instruments called goniometers. The 
common goniome- 
ter, which is here \L/ 
figured, consists of 
a light semicircle 
of brass, accurately 
graduated into de- 
grees, and having a 
pair of steel arms 
moving on a central 
pivot, and so arrang- 
ed as to slip in a 
groove over each other. The points a a can thus be made to 
embrace the faces of a crystal whose angle we wish to measure. 
When the edges of the sliding arms exactly fit the two faces 
containing the required angle, the screw which holds them 
together is tightened, and the graduated semicircle is applied 
with its centre at the point of intersection, when the angle is 
directly read on the arc, or its supplement is given in the 
alternate angles. By this instrument angles can be measured 
with only tolerable accuracy ; but where the greatest nicety 
is required, a much more delicate instrument is used. 

229. Wollaston's Reflective Goniometer. — The principle 




What is the law of cleavage ? 228. What is a goniometer ? Ex- 
plain the common one and its use. 229. Explain the principles of 
Wollaston's goniometer from the diagram. 



* From the Greek, gonia, an angle, and metron, measure., 



160 



CRYSTALLIZATION. 




of this instrument may be understood by reference to the 
annexed figure, which represents 
a crystal (o) whose angle (a b c) is 
required. The eye at P, looking 
at the face (b c) of the crystal, 
observes a reflected image of M, 
in the direction P N. The crys s 
tal may now be so turned that the 
same image is seen reflected in the 
next face, (b a,) and in the same direction, (P N.) To effect 
this, the crystal must be turned until a b has the present 
position of b c. The angle d b c measures, therefore, the 
number of degrees through which the crystal must be turned. 
But d b c subtracted from 180° equals the required angle of 
the crystal a b c ; consequently, the crystal passes through 
a number of degrees, which, subtracted from 180°, gives the 
required angle. When the crystal is attached to a graduated 
circle, which should move with it, we have the goniometer 

of Wollaston. In the annexed 
figure, a is such a circle of 
brass, graduated to half de- 
grees, and hung by the axis 
b, on which it moves with 
great steadiness. This axis 
is perforated from end to end 
for the passage of a closely 
fitting rod or central axis, on 
one end of which is the bent 
joint, (</,) carrying the crys- 
tal, (/.) By the head c, and 
the arrangement at rf, the 
crystal is adjusted without moving the graduated wheel ; and 
when this is accomplished in such a manner that the eye of 
the observer placed over the crystal, as at P, can see a clear 
image of a line on the wall, (M,) or a window-bar, in each 
face successively, then the graduated wheel (which stands 
when at rest at zero of the vernier e) is made to revolve, and 
with it the crystal, until the mark or window-bar is distinctly 
seen in the second face. The number of degrees and parts 
of a degree which correspond to the angle required, are thus 
obtained directly by the movement of the wheel, which was 




How is this principle used in Wollaston's instrument ? 



ISOMORPHISM. 161 

beforehand placed with 180° opposite to the zero on the 
vernier. The movement of the wheel is, therefore, in fact, a 
subtraction of the angle d b c from 180°. The great advan- 
tage of this instrument is, that we can by its aid obtain very 
precise results, and often on crystals too small to be held in 
the fingers and applied to a common goniometer. A small 
magnifier is sometimes attached to the instrument, to render 
it more complete. I 

230. In measurements by the goniometer, a knowledge of' 
the following simple principle in mathematics will be found 
of great value. " The sum of the three angles of a triangle 
equals 180°," or " The sum of the angles of a polygon equals 
twice as many right angles as the polygon has sides less 
two." If the figure has six sides, then it contains 2x (6 — 2) 
= 8 right angles, or 8 X 90=720°.* 

4. Isomorphism.^ 

231. Identity of crystalline form was formerly supposed 
to indicate an identity of chemical composition. We now 
know that certain substances may replace each other in the 
constitution of compounds, without changing their crystalline 
form. This property is called isomorphism, and those bases 
which admit of mutual substitution are termed isomorphous. 
Chemistry furnishes us many examples of these isomorphous 
bodies. Thus alumina and peroxyd of iron replace each 
other indefinitely. The carbonate of iron and carbonates of 
lime and magnesia are also examples, as the common sparry 
iron, {spathic iron,) which is a carbonate of iron, in which 
a large portion of carbonate of lime sometimes crystallizes, 
without producing any change of form in the mineral. Oxyd 
of zinc and of magnesia, oxyd of copper and protoxyd of iron, 
also take the place each of the other in compounds, without 
any alteration of crystalline form. When those bodies unite 

230. State the principles in this section regarding triangles and 
polygons. Give an example. .231. What is isomorphism? Name 
some examples. 

* The subject of crystallography cannot be further illustrated 
here ; but the learner who desires to pursue it is referred to th<» 
highly philosophical treatise on Mineralogy by Mr. J. J). Dana, 
from which we derive the substance of the foregoing. 

f Isos, equal, and morpke, form. 

14* 



162 CRYSTALLIZATION. 

with acids to form salts, the resulting compounds have the 
same crystalline form, and if they have the same color, are 
not to be distinguished from each other by the eye. 

In double salts, like common alum, these relations are 
also found. The sulphate of iron may take the place of 
sulphate of alumina in common alum, and no change of 
form will occur ; and soda may, in like manner, replace the 
potash. In fact, all the similar compounds of isomorphous 
bodies have a great resemblance to each other, in general 
appearance and chemical properties. The two bases in a 
double salt are, however, never taken from the same group 
of isomorphous bodies. 

232. A knowledge of this law is of great importance to the 
chemist, and often enables him to explain, in a satisfactory 
manner, apparent contradictions and anomalies, and to decide 
many doubtful points. It is supposed that the elements 
whose compounds are isomorphous, are also so themselves. 
M. Scheerer has noticed the curious and important fact, 
that in compounds containing magnesia, protoxyd of iron, 
and other bases of the 6th family below, a part of the base 
may be wanting without a change of crystalline form, pro- 
vided that this be replaced by a quantity of water which con- 
tains three times as much oxygen as this part of the base. 
For example, the compounds — 

Mg^i, Mg^i-f 3H and MgSi+6H, 

in accordance with this principle, are isomorphous. Thus, 
chrysolite and serpentine may be isomorphous, and much light 
is shed on the relations of hydrous and anhydrous minerals. 
A more full discussion of this subject does not belong to 
our restricted limits, and we can only mention, in conclusion, 
the group of isomorphous bodies name*d by Prof. Graham in 
his " Elements." 1st Family ; Chlorine, Iodine, Bromine, 
Fluorine. 2d Family ; Sulphur, Selenium, Tellurium. 3d 
Family ; Phosphorus, Arsenic, Antimony. 4th Family ; 
Barium, Strontium, Lead. 5th Family ; Silver, Sodium, 
Potassium, Ammonium. 6th Family ,* Magnesium, Manga- 
nese, Iron, Cobalt, Nickel, Zinc, Copper, Cadmium, Alumi- 
nium, Chromium, Calcium, Hydrogen. 



What of salts of isomorphous bases ? Is it found in double salts ? 
232. What six families of isomorphous bodies are named? 



ELECTRO-CHEMICAL DECOMPOSITION. 163 

233. Dimorphism* — Some substances have two forms, 
under both of which they are found. Thus common calc- 
spar (carbonate of lime) generally occurs in rhombohedrons, 
(224, 13,) but in arragonite (which is only pure carbonate 
of lime) it is seen as a rhombic prism, (221, fig 6.) 

III. CHEMICAL EFFECTS OF VOLTAIC ELECTRICITY. 
1. Electro- Chemical Decomposition. 

234. In discussing the electricity of chemical action, (158,) 
allusion was made to the power possessed by this species of 
electricity to produce or modify chemical decomposition. 
Having now become somewhat familiar with the elementary 
constitution of matter, and the laws of chemical combination, 
we can the more intelligently proceed to a very brief review 
of the chemical effects of voltaic electricity. 

235. Decomposition of Water. — Water was the first sub- 
stance on which the decomposing power of the battery was 
observed, soon after the discoveries of Galvani and Volta 
were made known in England. When two gold or platinum 
wires are connected with the opposite ends of the battery, and 
held a short distance asunder in a cup of water, a train of 
gas-bubbles will be seen rising from each, and escaping from 
the surface of the water. With an arrange- 
ment of two glass tubes placed over the plati- 
num poles, as figured in the margin, we can 
collect these bubbles as they rise, and shall 
soon find that the gas given off from the — 
plate is twice the volume of that obtained from 
the -f- plate. When the tubes are of the same 
size, this difference of volume becomes at once 
evident to the eye. By examining these 
gases, (as will be explained in the elementary 
chemistry,) we shall find them, respectively, 
pure hydrogen and pure oxygen, in the exact 
proportion of two volumes of the former to one of the latter, 
(190.) By no modification of the arrangement can we cause 

233. What is dimorphism? 234. Why is electro-chemical de- 
composition treated in this place ? 235. Mention the facts occurring 
in the decomposition of water. How is this made more striking ? 
In what proportion do the gases rise ? Can we change this pro- 
portion ? 

* From dis, two, and morphe, form. 




164< CHEMICAL EFFECTS OF VOLTAIC ELECTRICITY. 

this process to vary ; the hydrogen invariably appears on 
the — side, and oxygen on the + side. 

Water, then, is not only decomposed by the voltaic current, 
but that decomposition takes place in the proportions (185) 
of the equivalents of the elements, and these elements seek 
opposite poles of the battery. 

236. The experimental researches in electricity by Mr. 
Faraday , have shed much light on this subject ; and his 
views being now generally adopted, it will be unnecessary 
for us to discuss the opinions formerly advanced by Volta, 
Davy, and others, which are very interesting and important 
in the history of the science, but do not now form part of its 
first principles. Mr. Faraday's researches required the intro- 
duction of certain new terms, some of which we will now 
explain, as we shall find them more convenient than any 
others. (1.) The terminal wires or conductors of a battery 
are often termed the poles, as if they possessed some attractive 
power by which they draw bodies to themselves, as a magnet 
attracts iron. Mr. Faraday has shown that this notion is a 
mistake, and that the terminal wires act merely as a path or 
door to the currents, and he therefore calls them electrodes, 
from electron and odos, a way. The electrodes are any 
surfaces which convey an electric current into and out of a 
decomposable liquid. The term electrolyses, from electron, 
and the Greek verb luo, to unloose, is used to express decom- 
position ; and the substances suffering decomposition are 
termed electrolytes. Thus, the experiment mentioned in the 
last section is a case of electrolysis, in which water is the 
electrolyte. The elements of an electrolyte are called ions, 
from the Greek participle ion, going, since the elements go 
to the + or — electrode. The electrodes are distinguished 
as the anode and the cathode, from ana, upwards, and odos, 
way, or the way in which the sun rises; and kata, down- 
wards, and odos, or the way in which the sun sets ; the anode 
is +5 and the cathode — . We will now briefly consider the 

237. Conditions of Electro-Chemical Decomposition. — 
(1.) All compounds are not electrolytes, that is, they are not 
directly decomposable by the voltaic current. Many bodies, 

What do we infer ? 236. What is said of Faraday's researches ? 
What did they require? What does he call the poles, and why? 
Explain the terms electrode, electrolysis, and electrolyte. What 
are ions ? 237. Are all compounds electrolytes ? 



ELECTRO-CHEMICAL DECOMPOSITION. 165 

however, not themselves electrolytes, are decomposed by a 
secondary action. Thus, nitric acid is decomposed in the 
electrical circuit by the secondary action of the nascent (210) 
hydrogen, which, uniting with one equivalent of the oxygen, 
again forms water and nitrous acid. Sulphuric acid is not 
an electrolyte, while hydrochloric acid is ; and the nascent 
chlorine from the latter attacks the + electrode, if it be of gold. 
(2.) Electrolysis cannot happen unless the fluid be a con- 
ductor of electricity ; and no solid body, however good a 
conductor, has ever been thus decomposed. A plate of ice, 
however thin, interposed between the electrodes, will entirely 
prevent the passage of the power ; but the electrolysis will 
proceed as soon as the least hole melts in the ice, through 
which t-he power can pass. Fluidity is therefore a very 
essential condition of electrolysis. The fluidity may be that 
of heat, or of solution ; thus, the chlorids of lead, silver, and 
tin, are not electrolysed in a solid state, but when fused they 
are decomposed with ease. (3.) The ease of electro-chemi- 
cal decomposition seems in a good degree proportioned to the 
conducting power of the fluid. Thus, pure water is by no 
means a good conductor, and its electrolysis is difficult ; but 
the addition to it of a few drops of sulphuric acid, or of 
some other soluble conductor, greatly promotes the. ease with 
which it is decomposed. (4.) The amount of electrolysis is 
directly proportioned to the quantity of electricity which 
passes the electrodes. (5.) The binary compounds of the 
elements, (194,) as a class, are the best electrolytes. Water 
and iodid of potassium are instances ; while sulphuric acid, 
which has three equivalents of base to one of acid, is not an 
electrolyte. No two elements seem capable of forming more 
than one electrolyte. (6.) Most of the salts are resolvable 
into acid and base. Thus, sulphate of soda is resolved into 
sulphuric acid, which appears at the + electrode, and will 
there redden a vegetable blue ; and the soda which appears 
at the — electrode will restore the previously reddened blue ; 
so that by reversing the direction of the current, these striking 
effects are also reversed. 



Give examples. What is the second condition of electrolysis ? 
Give examples. (3.) To what is the ease of electrolysis pro- 
portioned ? (4.) To what is its amount owing ? (5.) What class 
of compounds are the best electrolytes I Give examples. (6.) What 
of salts ? Give examples. 



166 



CHEMICAL EFFECTS OF VOLTAIC ELECTRICITY. 



238. (7.) A single ion, as bromine, for instance, has no 
disposition to pass to either of the electrodes, and the current 
has no effect upon it. There can be no electrolysis except 
when a separation of ions takes place, and the separated 
elements go one to each electrode. (8.) There is no such 
thing, in fact, (as has been often supposed,) as an actual 
transfer of ions from one part of the fluid to either electrode. 
In the case of water, for example, (235,) oxygen is given out 
on one side and hydrogen on the other. In order that this 
may be the case, there must be water between the electrodes. 
We cannot believe that the separation of the elements takes 
place at the electrode where one element is evolved, and that 
the other travels over unseen to the opposite electrode. 

We may, however, conceive of 
water in its quiet state, as repre- 
sented by the annexed diagram, 
each molecule being firmly 
united by polar attractions 
(218) to every other, and that the electrolytic force of the 
electric current has power to disturb this polar equilibrium, 
each molecule being similarly affected. In this case the 
electrolysis will proceed from particle to particle through the 
whole chain of affinities, decomposing and recomposing, until 
the ultimate particle on each side, having no polar force to 

neutralize it, escapes at 



that electrode which has a 






© 



©. 



® 



©. 

^-^ s~^ -^ polarity opposite to itself. 

^J^J^L^JCfL) This explanation may be 
better understood, perhaps, 
by inspecting the second diagram, which represents a series 
of compound molecules of water undergoing electrolysis, the 
H and O being eliminated at the opposite extremities. The 
same explanation will be found to serve for all other cases of 
electrolysis, both simple and secondary. 

239. (9.) A surface of water, and even of air, has been 
shown capable of acting as an electrode, proving that the 
contact of a metallic conductor with the decomposing fluid is 
not essential. The discharge from a powerful electrical 

238. (7.) What is said of a single ton ? (8.) What of the transfer 
of ions ? Give the explanation offered of the decomposition of water. 
239. (9.) What is said of electrolysis without metallic con- 
ductors ? Explain /the experiment of the electrolysis of sulphate of 
soda by the electrical machine. 



ELECTRO-CHEMICAL DECOMPOSITION. 167 

machine (153) was made to pass from a sharp point through 
air to a pointed piece of litmus paper moistened with sulphate 
of soda, and then to a second piece of turmeric paper simi- 
larly moistened. This discharge had power to effect a true 
electrolysis ; the blue litmus was reddened by the sulphuric acid 
set free from the sulphate of soda, while the yellow turmeric 
was turned brown by the alkaline soda from the same salt. 

240. (10.) Electrolysis takes place in a series of com- 
pounds in the precise order of their equivalents. Thus if 
wine-glasses are arranged in a series, and in one is placed 
sulphate of soda, in another acidulated water, in another 
iodid of potassium, and in another hydrochloric acid, and if 
the whole series be connected together by siphon tubes, or 
moistened lampwick, passing from glass to glass, and a 
powerful galvanic current be then passed through them, 
electrolysis will occur in all, but not in an equal degree. 

It has been proved by accurate experiment, that the decom- 
position which ensues is in exact proportion to the equivalents 
of each substance. In other words, we may say it requires 
one equivalent of electricity to decompose one equivalent of 
an electrolyte, formed from the union of an equivalent of acid 
and another of base. Conversely, from the fact that an 
equivalent of electricity is required to decompose any com- 
pound, it is proved that the opposite elements of this compound, 
in uniting, will disengage the same equivalent of electricity. 

241. (11.) The passage of a current within the cells of a 
voltaic battery (262) depends also upon the decomposition in 
each cell, equally with that between the platinum electrodes. 
The same phenomena which we notice in the decomposing 
cell (235) take place also in each battery cell. Water is 
decomposed, and the hydrogen is given off from the positive 
plate, while the oxygen combines with the zinc, and thus 
escapes detection. Therefore, no fluid not an electrolyte is 
suitable to excite a battery. Acid water acts, for this purpose, 
only by the decomposition of the water, and oxydation of 
the zinc. The presence of the acid is useful only so far as 
it combines with the oxyd of zinc constantly accumulating on 



240. How does electrolysis occur in a series of compounds ? In 
other words, what do we say ? Conversely, what ? 241. How does 
a current pass in the cells of a battery ? What happens in each cell ? 
What is requisite in the fluid used to excite a battery ? How does 
acid water act in the battery ? 



168 



CHEMICAL EFFECTS OF VOLTAIC ELECTRICITY. 



(*) 




the zinc plate, which must be removed as fast as formed, in 
order to keep up a steady flow of electricity. 

242. From what has been said, we can see that a decom- 
posing cell interposed 
in the circuit will give 
us an exact account of 
the amount of electri- 
city flowing. Such an 
instrumeni has been 
called by Faraday a 
voltameter, (measurer 
of voltaic electricity,) 
and is figured in the 
margin, (a.) It diners 
from the decomposing 
cell, (235,) in being a 

single cell, and having a ground glass tube at 
top bent twice, so as to deliver the accumu- 
lating gases into a graduated air-vessel, in 
which their volume is measured. A more 
simple form of the apparatus is easily con- 
structed, as shown in b, which is a short piece 
with two corks and a bent tube, (t.) The 
electrodes p p pass through the corks, 
and should terminate in broad plates of 
platinum foil. A common form of the 
instrument is seen in the annexed figure, 
which has only one tube, and that is 
graduated. When this is filled with the 
mixed gases, and a lighted match is 
applied to the open end, the two elements 
unite again, with a loud explosion and 
vivid flash. If the apparatus is so 
arranged that this can be done over 
water without access of air, the fluid 
rushes up to fill the vacuum occasioned 
by the re-union of the elements in the 
formation of water. 

243. The theories which have been 
proposed to account for electro-chemical 



of glass tube, 




242. What is a voltameter ? What does it show ? Explain the 
figures. When the mixed gases are fired, what happens ? 




SUSTAINING BATTERIES. 169 

decomposition and the action of the voltaic circuit, we cannot 
discuss here, any further than to say that the chemical 
theory first proposed by Dr. Wollaston is now generally 
accepted. Volta argued that the contact of different metals 
was essential to the production of a current. The researches 
of Faraday, however, in confirming the chemical view of 
Wollaston, have completely disproved the contact theory. A 
very simple experiment by Faraday illustrates this statement. 
A slip of amalgamated sheet zinc bent at a right angle is hung 
in a glass of dilute acid ; on it is laid a folded piece ^-^ 
of bibulous paper moistened with iodid of potas- 
sium. A platinum plate, with an attached wire 
of the same metal, is now placed in the acid 
water, but not in contact with the zinc ; the 
sharpened end of the wire is bent, so as to touch 
the moistened paper, and very soon it is discolored 
by a brown spot made by the free iodine, liberated 
from the electro-chemical decomposition of the 
iodid of potassium, with which the paper is 
moistened. There is no contact of metals, and the current 
is excited only from the decomposition of the iodid out of the 
cell, and of the water in it. A very strong argument in 
favor of the chemical theory has been before mentioned, (161,) 
that the direction of the current is always determined by the 
nature of the chemical action — the metals most acted on 
being always positive. Professor Berzelius, in view of the 
facts of electricity, considers all chemical action as the result 
of opposite electrical states in the elements and their compounds. 
We have now made all the explanations that are necessary 
to enable us to understand the principles and construction of — 

2. Sustaining Batteries. 

244. Local action. — In the old forms of batteries made 
of copper and zinc unamalgamated, (164,) there is always 
a great amount of local action in each cell, arising from the 
impurity of the zinc. We have before explained how, by 
amalgamating the zinc w T ith mercury, it is reduced to a state 
of electrical uniformity, (161, note.) In order to have a 
constant voltaic current of equal power, not only the evils 

243. What two theories have been proposed to account for the 
electrical phenomena of electrolysis ? What simple experiment 
disproves the contact theory? 244, What are sustaining batteries? 
15 



170 



CHEMICAL EFFECTS OF VOLTAIC ELECTRICITY. 



r 



arising from local action must be avoided, but also, in some 
degree, the weakening of the acid solution. Batteries so con- 
structed as to meet these difficulties, are called sustaining 
batteries, or constant batteries. We will first mention 
245. DanielVs Constant Battery. — This truly philo- 
sophical instrument (a vertical section of 
which is annexed) is made up of an ex- 
terior circular cell of copper, ( + ,) three 
UIJ and a half inches in diameter, which serves 

both as a containing vessel and as a nega- 
tive element ; a porous cylindrical cup of 
earthen- ware, (P, fig. b,) (or the membrane 
of an ox-gullet,) is placed within the copper 
cell, and a solid cylinder of amalgamated 
zinc (— z) within the porous cup. The 
outer cell (c) is charged by a mixture of 
eight parts of water and one of oil of 
vitriol, saturated with blue vitriol, (sulphate 
of copper.) Some of the solid sulphate is 
also suspended on a perforated shelf, or in 
a gauze bag, to keep up the saturation. 
The inner cell is filled with the same acid water, but without 
the copper salt. Any number of cells so arranged are easily 
connected together by binding screws, as in the 
figure — the c of one pair to the % of tjie next, 
and so on. This instrument, when arranged 
and charged as here described, will give out no 
gas. The hydrogen from the decomposed water 
is not given off in bubbles on the copper side, as 
in all forms of the simple circuit of zinc and 
copper; because the sulphate of copper there 
present is decomposed by the circuit, atom for 
atom, with the decomposed water, and the 
hydrogen takes the atom of oxyd of copper, 
appropriating its oxygen to form water again, 
and metallic copper is deposited on the outer cell. 
No action of any sort results in this battery, 
when properly arranged, until the poles are 
joined. Ten or twelve such cells form the most active, 
constant, and least costly battery which can be procured. 




§45. Explain Daniell's Battery from the figure. What is its 
principle of action ? What becomes of the hydrogen ? When does 
ibis battery act ? 



SUSTAINING BATTERIES. 



171 




246. Grove's Battery. — Professor Grove, of London, has 
contrived another compound sustaining battery, of great power, 
and most remarkable intensity of action. The 
metals used are platinum and amalgamated zinc. 
A vertical section of this battery is shown in the 
annexed figure. The platinum ( + ) is placed in 
a porous cell of earthenware, containing strong 
nitric acid. This is surrounded by the amalga- 
mated zinc ( — ) in an outer vessel of dilute sul- 
phuric acid, (six to ten parts water to one of 
acid, by measure.) The platinum, being the 
most costly metal, is here surrounded by the 
zinc, in order to economize its surface as much 
as possible. In this battery the hydrogen of the 
decomposed water on the zinc side enters the nitric acid cell, 
decomposes an equivalent of the acid, forming water with 
one equivalent of its oxygen, while the deutoxyd of nitrogen 
is given out as a gas, and coming in contact with the air is 
converted into nitrous acid fumes. No other form of battery 
can be compared with this for intensity of action. A series 
of four cells (the platinum foil being only three inches long 
and half an inch wide) will decompose water with great 
rapidity ; and twenty such cells will evolve a very splendid 
arch of light from points of prepared charcoal, and deflagrate 
ail the metals very powerfully. It is rather costly, and 
troublesome to manage, as are all batteries with double cells 
and porous cups. The author has contrived a very efficient 
form of the same battery, in which mineral carbon (plumbago) 
is substituted for the platinum ;* and the carbon battery of 
Bunsen is constructed on the same principles, and produces 
most brilliant effects. But all other batteries yield in sim- 
plicity and ease of management to that contrived by Mr. 
Smee. 

247. Smee's Battery is formed of zinc and silver, and 
needs but one cell and one fluid to excite it. The silver 
plate (S) is prepared by coating its surface with platinum, 
thrown down on it by a voltaic current, in the state of fine 



246. What is Grove's Battery ? How does it differ from the last ? 
How does it act ? What is its energy ? 247. What is Smee's 
Battery ? 



* American Journal of Science, (1st series,) vol. xliii, p. 393. 



172 



CHEMICAL EFFECTS OF VOLTAIC ELECTRICITY. 



division, which is known as platinum-black. The object of 
this is to prevent the adhesion of the liberated hydrogen to 
the polished silver. Any polished smooth surface of metal 
will hold bubbles of gas with great obstinacy, thus preventing 
^ in a measure the contact between the fluid 

Jj and the plate by the interposition of a film 

of air-bubbles. The roughened surface 
produced from the deposit of platinum - 
black entirely prevents this. The zinc 
plates (z z) in this battery are well amal- 
gamated, and face both sides of the silver. 
The three plates are held in position by a 
clamp at top, (&,) and the interposition of 
a bar of dry wood (w) prevents the passage 
of a current from plate to plate. Water, 
acidulated with one-seventh its bulk of oil 
of vitriol, or, for less activity, with one- 
sixteenth, is the exciting fluid. The quantity of electricity 
excited in this battery is very great, but the intensity is not 
as great as in those compound batteries just described, where 
there is a double electrolysis, and of course a double intensity 
acquired. This battery is perfectly constant, does not act 
until the poles are joined, and, without any attention, will 
maintain a uniform flow of power for days together. A plate 
of lead, well silvered, and then coated with platinum-black, 
will answer equally as well, and indeed better than a thin plate 
of pure silver. This battery is recommended over every 





other for the student, as comprising the great requisites 
of cheapness, ease of management, and constancy. A 



How is the silver plate prepared ? What is the use of the pla- 
tinum-black ? How is this battery excited ? What acts as well as 
silver ? What recommends this battery over others ? 



ELECTROMETALLURGY. 173 

form of it, well calculated for the student's laboratory, is here 
shown, which is a porcelain trough with many cells. This 
battery is the one universally employed in electro-metallurgy. 

3. Electro-metallurgy. 

248. The depositing of metals by electrical agency 
seems to have been suggested by DanielPs battery. It has 
been remarked, that the copper of the sulphate of copper in 
the outer cell of that battery is deposited in a metallic state. 
The procuring of a pure metal in a perfectly malleable state, 
by means of a current of electricity, is a most important 
fact, and has given rise to a new and valuable art, which is 
every day extending its applications. We thus accomplish, 
in fact, a cold casting of copper, silver, gold, zinc, and many 
other metals ; and a new field of great extent has been thus 
opened for the application of metallurgic 
processes. The very simple apparatus re- 
quired to show these results experimentally, 
is represented in the annexed figure. It is 
nothing, in fact, but a single cell of Daniell's 
battery. A glass tumbler, (S,) a common 
lamp-chimney, (P,) with a bladder-skin tied 
over the lower end and filled with dilute 
acid, is ail the apparatus required. A strong 
solution of sulphate of copper is put in the 
tumbler, (S,) and a zinc rod (Z) in P ; the 
moulds, or casts, (m, m,) are seen suspended 
by wires attached to the binding screw of Z. Thus arranged, 
the copper solution is slowly decomposed, and the metal is 
evenly and firmly deposited on m, m. A perfect reverse 
copy*bf m is thus obtained in solid malleable copper. The 
back of m is protected by varnish, to prevent the adhesion 
of the metallic copper to it. In this manner the most elabo- 
rate and costly medals are easily multiplied, and in the most 
accurate manner. In practice, casts are made in fusible 
metal of the object to be copied, and the operation is con- 
ducted in a separate cell, containing only the sulphate of 
copper, one of Smee's batteries supplying the power. The 

248. What first suggested electro-metallurgy ? What is required 
in order to obtain several metals in the metallic state ? Explain 
Ihe process for obtaining the copy of a medal. 

15* 




1'74 CHEMICAL EFFECTS OF VOLTAIC ELECTRICITY. 

art is also now extensively applied to plating in gold and 
silver from their solutions ; the metals thus deposited 
adhering perfectly to the metallic surface on which they are 
deposited, provided these be quite clean and bright. Many 
details in these processes, very needful to the successful 
practice of the art, are necessarily omitted here. The reader 
is referred for further information to Mr. Smee's excellent 
" Elements of Electro-Metallurgy," or Walker's M Electro- 
type Manipulation," re-published at Philadelphia. 

249. We have now finished our preliminary view of those 
great powers of nature, whose operations we see to a greater 
or less extent in every chemical process. It may be thought 
that we have devoted too large a space to the topics already 
discussed ; but the author is convinced, from long observation, 
that if the principles of chemical philosophy are well 
acquired by the student, but little difficulty will be experienced 
in afterwards pursuing, even alone, and without the aid of a 
teacher, the wide detail of elementary chemistry. In entering 
on the execution of the remaining portion of our task, it is 
with the full understanding that no attempt is made on our 
part at presenting even a complete outline of the countless 
facts of elementary chemistry. Only such selections will be 
made from them as are deemed most in point to illustrate and 
enforce the principles already laid down, and to increase our 
familiarity with the philosophy of chemistry. It is hoped 
that this course will be satisfactory to both teacher and pupil, 
and the apology implied in this remark is intended to explain 
any apparent deficiencies which may be seen on the suc- 
ceeding pages. The complete and philosophical treatises 
of Turner, Kane, and Graham, are all excellent works of 
reference for the more advanced student. 

249. What is said of the importance of chemical philosophy? 



PART III.— INORGANIC CHEMISTRY. 

CLASSIFICATION OF ELEMENTS. 

250. A natural order and perspicuous classification is of 
the greatest service to the student in any department of 
science. We will not discuss the various modes which have 
been adopted in chemistry for arranging the elementary 
bodies and their compounds, since such discussions can have 
but little value while we are unacquainted with the characters 
and affinities of the bodies which we propose to classify. 
It is usual to divide elementary bodies into two great groups, 
the non-metallic and metallic elements. This convenient 
arrangement is founded on characters which in a general and 
popular sense are correct and easily distinguished, but which 
fail in several cases to afford any accurate distinction. No 
one can doubt to which classes, for example, gold and sulphui 
should be respectively referred ; but it is impossible to say 
why carbon and silicon are not as well entitled to be classed 
in the same group with the metals as tellurium and arsenic, 
if we except the single character of lustre. While there- 
fore we retain these general divisions, we should not hesitate 
to depart from them whenever by so doing we can present 
the facts of elementary chemistry in a clearer and more im- 
pressive manner. 

We will discuss the first division of elementary bodies in 
the following order : — 

SThe only element which forms com- 
pounds with all others, 
electro-negative bodies. 

Four elements very similar in all their 
sensible properties, and forming similar 
compounds with the metals, and whose 
acid compounds with oxygen, are also 
similar, and have the constitution ex- 
pressed by RO, R0 4 , R0 5 , R0 7 .* 

250. What is the value of classification in science ? What is 
necessary in order to understand a classification ? How are the ele- 
ments usually divided ? What is said of this division ? What exam 
pies are quoted in illustration ? Give the classification in the text. 
Name the bodies in the second class. Why are they associated ? 

* R signifies an atom of either of the electro-positive bodies. 



Class i. < 1. Oxygen. [• pounds with all others, and the type of 



Class ii. 



2. Chlorine, 

3. Bromine, 

4. Iodine, 

5. Fluorine. 



176 



INORGANIC CHEMISTRY. 



Class hi. < 



6. Sulphur, 

7. Selenium, 

8. Tellurium. 



Class iv. 



9. Nitrogen, 
10. Phosphorus. 



These stand in close relation with the 
preceding, while their compounds with 
the metals are more similar to the oxyds 
of those metals than are the analogous 
compounds of the second class. The oxy- 
gen acids have the formula RO2, RO3. 



This group properly includes also 
arsenic and antimony, which are, how- 
ever, from convenience, discussed else- 
_ where. The four form similar com- 
j pounds with oxygen, RO, R0 3 , R0 5 , 
I and peculiar gaseous compounds with 
J hydrogen, RH3. 



Class v. 



Class vi. 



11 Carh n 1 These three bodies are similar, non-vola- 
12* STc^' \.^ e > comD ustible bases, and alike in form- 
1S* Boron ' ' * n ° ^ ee ^ e ac ids with oxygen, having the 
J formula R0 3 . 

1 This highly electro-positive body is 
14 Hvdroffen l un ^^ e any of the preceding, and has 
. * y & • r analogies with the succeeding group 
[ J of metals. 

251. We will consider these several classes separately. 
The compounds which each element forms with those before 
it, will be taken up in order ; and we shall then be better able 
to understand the relation of each element to its associates 
in the same group. The several classes, too, will then 
be better understood in the analogies which unite, and the 
differences which separate them. 

CLASS I. 

1. OXYGEN. 

Equivalent, 8. Symbol, O. Density, 1*105. 

252. History and Importance. — This gaseous element 
was first discovered by Dr. Priestly, in 1774, and in the 
following year by M. Scheele, a Swedish chemist. Before 
this discovery, all gaseous bodies were considered as modifi- 
cations of common air, and oxygen was called vital air, 

What bodies form the third class? What other two bodies 
properly belong in the fourth class ? How are these all related ? 
What of their hydrogen compounds ? What bodies are associated 
in the fifth class ? What element stands alone in the seventh class ? 
What are its affinities? 251. How will they be discussed ? 252. 
When and by whom was oxygen discovered ? 



OXYGEN. 



177 



dephlogisticated air, &c. But Lavoisier proposed the name of 
oxygen,(Crom oxus, acid,) as bethought it the parent of all acids. 
This is the most interesting and important of the elements. 
It forms more than one-fifth part of the atmosphere, and 
eight-ninths of the waters of the globe by weight, and consti- 
tutes at least one-third part of the crust of the planet. By 
its means combustion and life are sustained, and it has the 
widest range of affinities of all known substances. 

253. Preparation. — This gas may be obtained pure from 
many substances which contain it ; but it is most easily and 
economically prepared by the decomposition, by heat, of the 
salt called chlorate of potash. Chloric acid contains five 
equivalents of oxygen, and the composition of the salt which 
it forms with potash is C10 5 , KO # . By heat, all the oxygen, 
both in acid and base, (six equivalents,) is given off, and 
we have left KC1, or the dry chlorid of potassium. The 
arrangement of apparatus for this purpose is shown in the 
annexed figure. One- 
tenth part by weight 
of pure oxyd of man- 
ganese is mingled with 
a convenient portion 
of chlorate of potash 
in a small glass flask, 
(a,) to which a bent 
glass tube is fitted by 
a cork. This tube 
conveys the gas to the 
open mouth of the in- 
verted air-jar, which is 
filled with water. The heat of the lamp beneath decom- 
poses the salt, and pure oxygen gas is freely given off, which 
escapes through the tube and displaces the water from the 
air-jar. By aid of the oxyd of manganese, the chlorate is 




What is said of its abundance and importance ? In what pro- 
portion does it exist in air, water, and the earth ? 253. How do we 
obtain pure oxygen ? Explain the use of manganese with the chlo- 
rate. Why is the chlorate of potash able to yield so much oxygen ? 

* One ounce of chlorate of potash will yield 543 cubic inches of 
pure oxygen gas, or more than 1| gallons. The constituents are 
in equivalent proportion, Chlorine 35-41, Potassium 39-19, and 
Oxygen 48. 



78 NON-METALLIC ELEMENTS. 

quietly decomposed, and the gas comes over gradually ; while 
without it the operation proceeds with almost explosive 
energy, the whole gas being given off at nearly the same 
instant. The glass flask (a) is protected from fusion by the 
thin metallic cup (c), in which is some dry sand. 

254. Oxygen is often made also from the peroxyd of 
manganese, heated strongly in a gun-barrel or iron bottle, 
from which a tube conveys the gas to the water-trough, or 
gas-holder. The gas from this source is not quite pure, 
having usually a little carbonic acid with it. One pound of 
peroxyd of manganese will yield about seven gallons of 
oxygen gas, and the process is recommended by its cheap- 
ness. Oxygen gas is also conveniently obtained by the 
action of sulphuric acid on the peroxyd of manganese, in 
which case an apparatus similar to that above figured is 
employed. Many other substances yield oxygen, as the 
oxyds of lead and mercury, or the nitrates of potash and 
soda, when heated alone in a suitable vessel. Bichromate of 
potash with sulphuric acid may also be employed for the 
same purpose. 

255. Properties and Experiments. — Oxygen, when pure, 
is a transparent, colorless gas, which no degree of cold or 
pressure has ever reduced to a liquid state. It is a little 
heavier than the atmosphere, its density being, compared to 
air, as 1*1057 : 1*000. One hundred cubic inches of the dry 
gas (32 and 49) weigh 34*29 grains. Its most remarkable 

O property is the energy with which it supports com- 
bustion. Any body which will burn in common air, 
burns with greatly increased splendor in oxygen gas. 
A newly extinguished candle or taper, which has the 
least fire on *the wick, will instantly be rekindled in 
oxygen, and burn in it with great beauty. A quart of 
this gas in a narrow-mouthed bottle, will easily relight 
a candle fifty times. A bit of charcoal bark with the 
least spark of ignition on it, attached to a wire and 
lowered into a jar of this gas, will burn with intense 
brilliancy as long as any of the gas remains. A steel 
watch-spring tipped with a piece of burning match, and 
lowered into a jar of pure oxygen gas, bursts into the most 



254. How is oxygen made from manganese ? What is the yield ? 
What other modes are mentioned ? 255. Describe the properties 
of oxygen Explain the combustion of the watch-spring. 



OXYGEN. 



179 




magnificent combustion ; the oxyd of iron which is formed 
falls down in burning globules, like 
glowing meteors, which fuse them- 
selves into the glazed surface of an 
earthen plate, (as in the figure,) 
although covered with an inch of 
water. If, as often happens, a 
motion of the spring throws a glo- 
bule of this fused oxyd against tfye 
side of the glass vessel, it melts 
itself into the substance of the glass, 
or if that is thin, goes through it. 
This is one of the most brilliant and 
instructive experiments in chemistry. 
If the orifice at top is closeclair-tight, and water is poured 
into the plate from a pitcher? we shall find, as the experiment 
proceeds, that the water will rise in the jar as the gas is 
consumed ; and if we could collect and weigh the globules of 
oxyd of iron, we should find in them an increase of weight 
equal to the weight of the oxygen consumed. 

256. It affects life when breathed, by quickening the 
circulation of the blood, and causing an excitement, which 
soon results in general inflammatory symptoms and death. 
In an atmosphere of pure oxygen we should live too fast. It 
exerts, however, no specific poisonous influence, being, when 
used in moderation, altogether salutary, and often resorted to, 
to inflate the lungs of drowned persons, and not unfrequently 
with the most beneficial results. The blood is constantly 
brought into contact with the air in thejuqgs, and it is the 
oxygen in the air which is the active agent in rendering it fit 
to sustain life. As this is the first gaseous body we have had 
occasion to mention, we will make a few remarks on the 

i 
Management of Gases. 

257. Pneumatic Troughs. — Gases not absorbed by watei, 
are always collected in a vessel of water called a pneumatic 
trough ; the figure in 253 shows a small neat one made of 
glass ; but for practical purposes they are usually made, like 
the one on the next page, of japanned copper, of tin plate, 



256. How does oxygen affect life ? 
257. What is a pneumatic trough ? 



Is it poisonous or salutary ? 



180 



NON-METALLIC ELEMENTS. 




or wood, to hold several gallons of water. The essential 

parts are the well (W) 
in which the air-jars are 
filled, and a shelf (S) 
covered with about . an 
inch of water. A groove 
or channel (d) is made 
in the shelf, to allow the 
end of the gas-pipe to 
dip under the air-jar. 
If nothing better is at 
hand, a common wooden tub or water-pail, with a perforated 
shelf and inverted funnel, will answer for small operations. 
Learners are sometimes puzzled to tell why the water will 
stand in an air-jar above the le^el of the cistern. A moment's 
thought, however, on the principles of atmospheric pressure 
(24) already explained, will make this clear. We must 
remember, too, that gases are only light fluids, and must be 
poured upwards, by the same laws which require fluids 
heavier than air to be poured downwards. 

258. To store large quantities of gases, capacious vessels 
of copper or tinned iron are used, which are called gas- 
holders. These vessels are made frequently to hold 30 to 50 
gallons. The simplest form is that cff a large air-jar, pro- 
vided with stop-cocks at top for the entrance and escape of 
the gas, and contained in an exterior cask of water. A 
more convenient gas-holder for some 
purposes is that contrived by Mr. Pepys, 
a section of which is shown in the 
annexed figure. It is a tight cylinder 
of copper or tin (.g), with a shallow pan 
of the same metal supported above it by 
several props, two of which are tubes with 
stopcocks, (a b.) Near the bottom is a 
large orifice (o) for receiving the gas. To 
use this instrument, it is first filled with 
water by closing the lower orifice (o) with 
a large cork, and opening all the upper 
ones, (a b s.) Water is then poured into the shallow pan (p), 
until it runs out at s, which is then closed, and the remainder 




How are gases poured ? 258. What is a gas-holder ? Describe 
Pepys' gas-holder. How is the gas introduced ? 




CHLORINE. 181 

of the air escapes through b ; when it is full, the cocks (a b) 
are shut, and the lower orifice being then opened, the water, 
sustained by the pressure of the air, cannot escape except as 
it is driven out by the entrance of the gas at o, from which 
the water escapes as fast as the gas enters. When used, the 
gas-holder must stand over a tub, to catch the water which is 
driven out at o. The gas is obtained for use by drawing it 
off from the orifice (s or b) at the same time that the shallow 
pan (p) is full of water, and the cock (a) open. The tube 
to which this cock is attached goes 
nearly to the bottom of the gas-holder, 
and the pressure of the water in the 
pan will force out the gas from any 
other open orifice in the gas-holder as 
soon as the cock (a) is opened. An 
air-jar is easily filled with gas from the 
holder by placing it full of water in the 
upper pan, (see annexed figure,) over 
the orifice (b) ; on turning the two stopcocks, (a, b,) the gas 
issues from b and fills the jar, while the water of the jar 
runs down the pipe (a) to supply the place of the gas. 

In collecting gas, the precaution should never be neglected 
of first allowing all the atmospheric air to escape from the 
vessels, before any of the gas is saved for use. 

Bags of India-rubber cloth are prepared by the instrument- 
makers as gas-holders, which can be used without the incon- 
venience of employing water. 

259. Gases which are absorbed by water may be collected 
over mercury ; but this is an expensive method, because of 
the high cost of the fluid metal. Some gases, — as chlorine, 
for instance, — act on the mercury, forming compounds with it. 
We may better collect the absorbable gases in clean dry 
vessels by displacement of air, as is explained by the figure 
in the next section. 

CLASS II. 

2. CHLORINE. 

Equivalent, 35*41. Symbol, CI. Density, 2*47. 

260. History and Preparation. — This very remarkable 
element was first noticed by the Swedish chemist, Scheele, 

How is it prepared for use ? What precaution is to be observed in 
collecting gases ? 259. How are absorbable gases collected? 260. 
When and by whom was chlorine discovered ? 
16 



182 



NON-METALLIC ELEMENTS. 



in 1774, while examining the action of hydrochloric acid on 
peroxyd of manganese. For a long time it was supposed to 
be a compound body, but it is now known to 
be simple. It is best obtained by the action 
of two parts of hydrochloric acid on one 
part of powdered peroxyd of manganese. 
The materials are mingled in a capacious 
flask, and the apparatus arranged as in the 
figure. A drop or two of oil of turpentine 
is added to the mixture, to prevent the 
frothing up of the materials. The heat of 
a lamp, or pan of coals, causes the gas to 
pass over freely by the bent tube to the 
bottom of a dry bottle. This gas, being 
much heavier than the air, displaces it 
completely ;' and when the bottle is filled, 
(which we discern by the greenish color of 
the gas,) a greased stopper is tightly fitted 
to it, and another bottle substituted. In 
this way a number of bottles may very 
conveniently be filled and kept for use. 
A card, with a cleft on one side surrounding the tube, serves 
to shut out fluctuations of the air while the bottle is filling. A 
strong solution of common salt (brine) does not absorb chlo- 
rine, and may be usefully employed in some cases to collect 
this gas in a small porcelain or other trough. It can also be 
collected with but little loss in vessels filled with hot water. 

In this process the affinities are between the manganese, 
for one equivalent of the chlorine in the acid, forming chlorid 
of manganese, and between the oxygen of the manganese 
and the hydrogen of the acid, forming water. The following 
symbols will render this more clear : we take 

Mn0 2 and 2HC1, and obtain Mn CI, 2HO, and CI. 
The last equivalent of chlorine, having nothing to detain it, 
is given off. Chlorine exists abundantly in sea-water and 
common salt, in union with sodium. 

Pure chlorine is also easily obtained by acting on one part 
of powdered bichromate of potash, in a small retort, with six 




How is this gas obtained ? Explain its collection by displacement. 
How else is it collected ? Explain the affinities which act in the 
collection of chlorine. What other method is named for procuring 
chlorine ? 



CHLORINE. 183 

parts of strong hydrochloric acid. A gentle lamp heat is 
required to begin the process, which then goes on without 
further application of heat, yielding abundance of gas. 

261. Properties. — Chlorine is a greenish-yellow gas, 
(whence its name, from chloros, green,) with a powerful and 
suffocating odor, and is wholly irrespirable. Even when 
much diluted with air, it produces the most annoying irritation 
of the throat, with stricture of the chest, and a severe cough, 
which continues for hours, with the discharge of much thick 
mucus. The attempt to breathe the undiluted gas would be 
fatal ; yet, in a very small quantity, and dissolved in water, 
it is used with benefit by patients suffering under pulmonary 
consumption. 

Under a pressure of about four atmospheres it becomes a 
limpid fluid of a fine yellow color, which does not freeze at 
zero, and is not a conductor of electricity. It immediately 
returns to the gaseous state with effervescence on removing 
the pressure. 

Water recently boiled will absorb, if cold, about twice its 
bulk of chlorine gas, acquiring its color and characteristic 
properties. The moist gas exposed to a cold of 32° yields 
beautiful yellow crystals, which are a definite compound of 
one equivalent of chlorine and ten of water, (CUOHO.) If 
these crystals are hermetically sealed up in a glass tube, 
they will, on melting, exert such a pressure as to liquefy a 
portion of the gas, which is distinctly seen as a yellow fluid 
not miscible with the water which is present. Chlorine is 
one of the heaviest of the gases, its density being 2*47, and 
100 cubic inches weighing 76*5 grains. 

262. Its bleaching power is its most remarkable property, 
and a most valuable one in the arts, in bleaching rags for 
paper, and in whitening linen and cotton goods. For these 
purposes, it is procured in large quantities by the action of 
oil of vitriol on a mixture of common salt and manganese. 
Either the gas is used directly, or its solution in water, or 
its compound with quicklime, known as " bleaching powders." 
It is easy to see its power in discharging colors, by bleaching 



261. Describe chlorine. How does it affect respiration? Under 
what pressure does it become fluid ? How does cold water affect it ? 
When moist chlorine is cooled, what happens ? What is the density 
of chlorine, and weight of 100 cubic inches? 262. What is its 
most remarkable property ? How is it used for this purpose ? 



184 NON-METALLIC ELEMENTS. 

some scraps of calico and common writing on paper, in a 
wine-glass, by the solution of the gas in water. Dry chlo- 
rine does not bleach, moisture being essential to this process. 

263. The disinfection of offensive apartments, sewers, 
and other like places, is rapidly accomplished by chlorine, 
and no other substance is in this respect equal to it ; but care 
is required not to use too much of it in apartments which are 
inhabited. The bleaching powder, mixed in shallow vessels 
with water, is sufficient for most purposes of this nature. 

264. Double Condition, or Allotropism of Chlorine. — 
Chlorine can exist in two states, — an active and a passive 
state. The first is its condition as ordinarily known, when 
prepared in day-light. If an aqueous solution of chlorine 
be prepared as before mentioned, in recently boiled water, 
and a part of it be exposed in an inverted bulb to the direct 
rays of the sun, or a strong daylight, while another portion, 
as soon as prepared, without exposure to light, is set aside in 
a dark closet, and in a similar vessel, we shall find them 
very differently affected. That which was in the dark will 

C>. have undergone no change, while that in the sun-light 
jj will have suffered decomposition ; a notable quantity of 
^ nearly pure oxygen will have collected in the bulb, as 
shown in the annexed figure, and hydrochloric acid 
will have been formed in the fluid from the union of 
the chlorine and the hydrogen of the water, whose 
oxygen is set free. The rapidity of this decomposition 
of water by the chlorine depends on the quantity of the sun's 
rays and the temperature, and being once begun, it continues 
afterwards even in the dark. Mere increase of temperature 
does not, atone, cause the decomposition, although it aids it. 
Some time elapses after the chlorine water is exposed, before 
it begins to be decomposed, during which the chlorine is 
undergoing its specific change. The indigo rays (65) are 
chiefly instrumental in producing this effect, and impart to 
chlorine an activity which it does not possess when kept in the 
dark. The relations of chlorine to light are very interesting 
and important, and we shall have something more to say 
about them under hydrogen. Chlorine, as we shall see, is not 
the only element which is known to us in a double condition. 



Does dry chlorine bleach ? 263. How does it affect bad odors ? 
264. Explain what is said of the double condition of chlorine, and 
the effect of light on it. 



CHLORINE. 185 



Compounds of Chlorine with Oxygen. 

265. Chlorine has comparatively little affinity for oxygen, 
being too closely allied to it in general properties to form 
very stable combinations with it. Its strongest affinity is for 
hydrogen and the metals. A lighted candle will burn with a 
diminished flame in a vessel of chlorine, and an abundant 
cloud of black smoke is given off, being the carbon of the 
flame, which cannot burn in chlorine. A rag or bit of paper 
wet in oil of turpentine, and held in the mouth of a bottle of 
chlorine, is inflamed, while the interior of the vessel is coated 
with a brilliant black varnish of carbon derived from the oil. 
In these cases the chlorine combines with the hydrogen of 
the combustible body, and not with the carbon. Powdered 
metallic arsenic, antimony, and some other metals, are in- 
flamed in chlorine gas, being converted into chlorids. Phos- 
phorus is also spontaneously inflamed in chlorine, burning 
with a pale yellowish-white light. The strong affinity of 
chlorine for hydrogen is shown (264) by its power of decom- 
posing water in the sun's light. The bleaching power of 
chlorine is due probably to its affinity for hydrogen. Printers' 
ink, of which carbon is the basis, is not decolorized by 
chlorine. 

266. Chlorine unites with oxygen only by circuitous 
means, and forms with it four compounds, as follows : 

Composition by weight. 

Svmbol. 
Hypochlorous acid, 
Chlorous acid, 
Chloric acid, 
Hyperchloric acid, 

267. Hypochlorous Acid, (Euchlorlne.) — This body is 
always formed when chlorate of potash is acted on by hydro- 
chloric acid, but when thus produced is almost instantly 
resolved into chlorous acid and chlorine. The best way to 
procure it is to pass a gentle stream of dry chlorine gas over 



265. How are chlorine and oxygen affected to each other ? How 
does chlorine affect burning bodies, as a candle ? Why is turpentine 
inflamed in it? How does it affect other bodies? 266. Name the 
compounds of oxygen and chlorine, and their constitution. 267. 
How is hypochlorous acid formed ? 

16* 



Symbol. 


Chlorine. 


Oxygen. 


CIO 


35-41 


8 


CIO4 


35-41 


32 


C10 5 


35-41 


40 


C10 7 


35-41 


56 



186 



NON-METALLIC ELEMENTS. 




red precipitate, (the oxyd of mercury prepared by precipi- 
tation,) contained in 
an apparatus similar 
to the annexed fig- 
ure. The chlorine 
is evolved in the gas- 
bottle, (&,) and passes 
by a bent tube to a 
long horizontal tube 
(0 filled with tho 
red precipitate, with 
which it forms chlo- 
rid of mercury,which 
remains in the tube, while hypochlorous acid (CIO) is 
evolved as a gas, and is collected in a by displacement of air. 

268. This gas is of a yellowish-green color, much 
resembling chlorine; water rapidly absorbs 100 times its 
own volume of it. It is easily exploded by heat, oxygen 
and chlorine being the result. At zero it is condensed into a 
deep red liquid, which is slowly dissolved by water. It acts 
more corrosively on the skin than nitric acid, and bleaches 
powerfully. Its aqueous solution is very unstable, being 
decomposed by light, and even by agitation with irregular 
bodies, as broken glass. Hypochlorous acid is one of the 
most powerful oxydizing agents known, especially in raising 
sulphur and phosphorus to their highest state of oxydation, 
a result which only strong nitric acid can accomplish. The 
euchlorine of Davy is a mixture of chlorine and chlorous 
acid, and not a protoxyd of chlorine, as was supposed. 

269. Chlorous acid, C10 4 . — This body is obtained by 
the action of sulphuric, or of hydrochloric acid, on chlo- 
rate of potash. For this purpose a little of the salt, in a 
small glass retort, is covered with diluted sulphuric acid, 
(I acid and £ water, cooled,) or with its bulk of hydrochloric 
acid, and gently heated by a warm water bath. A deep 
yellow gas is evolved, which may be collected like chlorine, 
by displacement of air in dry vessels. It is exceedingly 



Explain the apparatus. 268. What are the properties of this 
gas ? How does its aqueous solution behave ? Has it bleaching 
properties ? How are its oxydizing powers ? 269. How is chlo- 
rous acid obtained ? Describe its properties. How does it affect 
combustibles ? 



CHLORINE. 187 

explosive, and will not bear the heat of boiling water without 
being forcibly resolved into its elements. A rag wet with 
oil of turpentine at once explodes it. It is composed of two 
volumes of chlorine and four volumes of oxygen, condensed 
into four volumes. It is largely dissolved by water, forming 
a rich yellow solution with bleaching properties. It forms a 
series of salts with the alkalies, and is capable of com- 
pression into a liquid. 

270. If strong sulphuric acid is poured upon a small 
quantity of crystals of chlorate of potash in a wine-glass, a 
violent crackling is heard, and the glass is soon filled with 
the heavy yellow vapors of the chlorous acid gas, which at 
once inflame a rag held over it wet with turpentine, with a 
smart explosion. If the chlorate of potash is mixed with 
sugar, a drop of sulphuric acid will inflame the mixture with 
a brilliant combustion. Phosphorus burns spontaneously in 
chlorous acid gas ; if sorfte small fragments of phosphorus 
are added to a glass of water at the bottom of which a few 
crystals of chlorate of potash have been placed, and sul- 
phuric acid is introduced by means of a long-tubed funnel to 
the bottom of the vessel, the salt is decomposed, and the 
phosphorus flashes under water, in the chlorous acid which 
is set at liberty. 

271. Chloric acid, C10 5 , is the most important compound 
of chlorine and oxygen. It is formed by passing chlorine 
gas through a solution of pure potash, to saturation ; on 
evaporating this solution, flat tabular crystals of a white salt 
are gradually formed, which are chlorate of potassa, while a 
chlorid of potassium remains in the solution. This important 
salt, as already mentioned, (253,) is a compound of chloric 
acid and potassa, (C10 5 KO.) The acid is obtained separate 
and pure with some difficulty, by decomposing a solution of 
chlorate of baryta by the requisite amount of sulphuric acid, 
and gradually evaporating the liquid to a syrup. In this 
state its affinity for all combustible matter is so great, that it 
cannot be kept for an instant in contact with any substance 
containing carbon or hydrogen. The chlorates are at once 

How does heat affect it ? 270. What happens when chlorate of 
potash is treated with strong sulphuric acid ? How is the com- 
bustion of phosphorus shown by it under water? 271. Describe 
the formation of chloric acid. What use has already been made by 
us of its compound with potash? What are its characteristic 
properties ? 



188 NON-METALLIC ELEMENTS. 

recognised by their powerful action on combustible matter, 
by yielding pure oxygen when heated, and by giving out the 
yellow chlorous acid when treated with sulphuric acid. 

3. BROMINE. 

Equivalent, 78*26. Symbol, Br. Density, in vapor, 5*93. 

272. History. — This element was discovered in 1826, by 
M. Balard, in the mother-liquor, or residue of the evaporation 
of sea-water. It is named from its offensive odor, (bromos, 
bad odor.) In nature it is found in sea-water combined with 
alkaline bases, and in the waters of many saline springs and 
inland seas. The salt springs of Ohio abound in the com- 
pounds of bromine, and it is found in the waters of the Dead 
Sea. The only use which has been made of bromine in the 
arts is in the practice of photography. It is also used in 
medicine. In a chemical point of view it is very interesting, 
from its similarity in properties, and the parallelism of its 
compounds to chlorine and iodine. 

273. Preparation. — The mother-liquor containing bromids 
is treated with a current of chlorine gas, which decomposes 
these salts, setting the bromine free, which at once colors the 
liquid of a reddish-brown color. Ether is added and shaken 
with the liquid, until all the bromine is taken up by the ether, 
which acquires a fine red color, and separates from the saline 
liquid. Solution of caustic potash is then added to the 
athereal solution, forming bromid of potassium and bromate 
of potash. This solution is evaporated to dryness, and the 
salts being collected are heated in a glass retort with sul- 
phuric acid and a little oxyd of manganese. The bromine 
distils over, (117,) and is condensed in a cooled receiver, 
into a red fluid. 

274. Properties. — Bromine somewhat resembles chlorine 
in its odor, but is more offensive. At common temperatures 
it is a very volatile liquid, of a deep red color, and with a 
specific gravity of 3, being one of the heaviest fluids known. 
Sulphuric acid floats on its surface, and is used to prevent its 
escape. At zero it freezes into a brittle solid. A few drops 

272. When, where, and by whom, was bromine discovered? 
Whence its name ? How is it found in nature ? What use is made 
of it? 273. Describe its preparation. 274. Describe its properties. 
How does it resemble chlorine ? 



IODINE. .89 

n a large flask will fill the whole vessel when slightly 
warmed, with blood-red vapors, which have a density of 
nearly 6-00, air being one. It is a non-conductor of elec- 
tricity, and suffers no change of properties from heat, or any 
other of the imponderable agents. It dissolves slightly in 
water, forming a bleaching solution. 

Bromine unites with oxygen, forming bromic acid. 
(Br0 5 ,) which is similar in all its actions to chloric acid. 



4. IODINE. 

Equivalent, 126-36. Symbol, I. Density in vapor, 8-7. 

275. History. — Like chlorine and bromine, this substance 
has its origin in the sea, being secreted by nearly all sea- 
weeds from the waters of the ocean. It was discovered in 
1811, by M. Courtois, of Paris, in the kelp, or ashes of sea- 
weeds. The common bladder sea-weed, (fucus vesiculosus,) 
and many other sea- weeds of our own coasts, abound in salts 
of iodine. It has been found in mineral springs rather 
abundantly, and in one or two minerals. In the arts its 
chief uses are for the photographic pictures, and lately it has 
been employed in France in the process of dyeing. In medi- 
cine it is of great value in glandular and other diseases. 

276. Preparation. — Kelp is treated with water, which 
washes out all the soluble salts, and the filtered solution is 
evaporated until nearly all the carbonate of soda and other 
saline matters have crystallized out. The remaining liquor, 
which contains the iodine, is mixed with successive portions 
of sulphuric acid in a leaden retort, and after standing some 
days to allow the sulphuretted hydrogen, &c, to escape, 
peroxyd of manganese is added, and the whole gently heated. 
Iodine distils over in a purple vapor, and is condensed in a 
receiver, or in a series of two-necked globes. 

277. Properties. — Iodine crystallizes in brilliant blue- 
black scales of a metallic lustre, somewhat resembling plum- 
bago. When slowly cooled from a state of dense vapor in a 
glass tube hermetically sealed, it crystallizes in acute octa- 



275. How is iodine found associated ? Who discovered it, and 
when ? What are its uses ? Does it unite with oxygen ? 276. 
How is it prepared ? 277. Describe its properties ? How does it 
crystallize ? 



190 NON-METALLIC ELEMENTS. 

hedrons with a rhombic base, (222.) The density of iodine 
is 3-948, (water = 1,) it melts at 225°, and boils at 247°, 
forming a superb violet vapor of unequalled beauty ; (hence 
its name, iodes, like a violet.) For this purpose a few grains 
of it may be volatilized in a bolt-head, (74,) or on a piece of 
heated brick. If a small portion is thrown into a red-hot 
platinum crucible, it at once assumes the spheroidal state, 
(135,) and will roll about in a liquid globule and give off 
very little vapor. If the crucible is then allowed to cool to 
about 220°, it suddenly bursts into a cloud of purple vapor, 
forming a most striking and instructive experiment. 

Iodine is almost insoluble in pure water, requiring 7000 
parts of water to dissolve one of iodine, or one grain to a 
gallon of water. Alcohol and ether dissolve it freely, and 
so do solutions of nitrate or hydrochiorate of ammonia, and 
of iodids. It temporarily stains the skin deep brown, and its 
odor reminds us of chlorine, but it is much less annoying. 

Iodine forms a deep blue compound with a cold solution 
of common starch, by which it may at once be detected, this 
being a characteristic test. In combination it may be de- 
tected by the same agent, if a little nitric acid or chlorine 
water is previously added to the fluid supposed to contain an 
iodid, whereby the iodine is set free. 

Compounds of Iodine with oxygen. 

278. Iodine unites with oxygen, forming iodic and 
hyperiodic acids. Their constitution is seen in the following 
formulas. 

Composition by weight. ' 



Symbol. Iodine. Oxygen. 

Iodic acid, I0 5 126-36 40 

Hyperiodic acid, IO? 126-36 56 

These acids are analogous to the chloric and perchloric 
acids. Iodic acid is formed by the action of strong nitric 
acid on iodine, and subsequent evaporation, to expel the free 
nitric acid remaining. It is a very soluble substance, and 
crystallizes in six-sided tables. 



Give its density in vapor, and as a solid its point of fusion. In 
what is it soluble ? By what easy test is it detected ? 278. What 
compound does it form with oxygen ? Give their composition and 
formulae. To what are these acids analogous ? What are the com- 
pounds of iodine and oxygen ? 



FLUORINE. 191 

279. Both bromine and iodine combine with energetic 
combustion or explosive violence with phosphorus, and 
several of the metals, forming bromids and iodids with such 
bases. Chlorine unites with iodine, forming two, and pos- 
sibly three distinct chlorids, (IC1, IC1 3 , and IC1 5 .) These are 
formed by the direct action of chlorine on dry iodine. There 
are also bromids of iodine of uncertain composition. 

5. FLUORINE. 

Equivalent, 18-70. Symbol, F. Density, 1-289. 

280. History and Properties. — This element has only 
very lately been obtained in a free state, although we have 
long known its compounds. Its remarkable energy of com- 
bination with the metals, and especially with silicon, which 
is a constituent of all glass, has rendered its isolation very 
difficult. Messrs. Knox, of Ireland, and Baudrimont, of 
France, have so far succeeded in effecting its separation as 
to leave no doubt of its being a yellowish-brown gas, having 
the smell and bleaching properties of chlorine. It does not 
act on glass, (as its compound with hydrogen does,) but 
unites directly with gold. Its specific gravity is 1-289. Its 
associations and characteristic properties all show most 
decidedly that it must be classed with this group of elements, 
and it is, in common with its associates, a powerful negative 
electric. Fluorine probably holds a place intermediate 
between oxygen and chlorine. The fact that it forms no 
known compound with oxygen shows how very similar in 
character it must be to that element. 

281. The compounds of fluorine, which we shall mention, 
nearly all belong to subsequent groups, although it forms no 
known compound with oxygen ; Mr. Leeson has recently suc- 
ceeded in combining it with iodine and bromine. When a mix- 
ture of fluor-spar with peroxyd of manganese and sulphuric 
acid is heated, a reaction takes place, by which fluorine in 
an impure form is disengaged. If the gas thus produced is 
passed through iodine suspended in water, combination takes 



279. How are bromine and iodine affected by phosphorus and the 
metals ? Does chlorine unite with iodine ? 280. What has pre- 
vented the study of fluorine ? What is known of it ? To what is 
it allied closely? Does it unite with oxygen? 281. What com- 
pounds of it are named in this section ? 



192 



SULPHUR. 



place, and a fluorid of iodine is formed, which crystallizes in 
yellow scales. A fluorid of bromine is formed by a similar 
process, which has been used in the photographic art with 
success. It is not crystallizable. The precise composition 
of these bodies is not known. 

CLASS III. 

■4- 6. SULPHUR. 

Equivalent, 16-09. Symbol, S. Density in vapor, 6*648. 

282. History. — Sulphur is one of those elements which 
have been known from the remotest antiquity. It occurs 
abundantly in many volcanic regions, as in the island of 
Sicily, the vicinity of Naples, and many islands of the 
Pacific. It is also found in beds of gypsum, as a rock, near 
Cadiz in Spain, and at Cracow in Poland. Its compounds 
with iron, copper, and other metals, are widely spread over 
the earth, and in combination as sulphuric acid it forms a 
large part of common gypsum or plaster of Paris. 

283. Properties. — It is a straw-yellow brittle solid at 
common temperatures, having a gravity of 1*98. 
In crystalline form it is dimorphous, (233.) Its 
usual form is the rhombic octahedron, (222,) as in 
the figure. Native sulphur has this form or its 
modification, and so has sulphur deposited in crys- 
tals from solution. But if it is fused (as in a 
crucible) and allowed to cool gradually, and the 
crust is broken before the whole of the interior mass 

is solidified, a part may be turned out, while the remainder 
has the form of long, slender, confused 
prisms, as in the annexed figure. This 
difference of form is the result of tempe- 
rature. Sulphur melts at 226°, and from 
that point to 280° is a clear amber-colored 
fluid. At about 320° it begins to thicken 
and grow reddish, and from that point to 
about 480° it is so stiff* that the vessel 
containing it may be turned over without spilling it. In this 
state it copies seals, medallions, &c, very perfectly, and is 



282. Give the natural history of sulphur. 283. What are hs 
principal properties ? Describe its crystallization and fusion. 





SULPHUR. 193 

much used for this purpose. At 482° it becomes more fluid, 
and remains so until it reaches its boiling point at 601°. It 
is very volatile, and sublimes readily even below its boiling 
point, forming flowers of sulphur. This is the method used 
to purify it from the earthy matters found with it. It is also 
cast into long cylinders, and is. then called roll sulphur. 
When cold it has no odor, and the warmth of the hand causes 
it to crackle, from a disturbance of its crystalline structure. 
By warmth and friction it acquires its well known brimstone 
smell. It is eminently a non-conductor of electricity, and is 
easily excited to give negative electrical sparks by friction. 

Sulphur is insoluble in water, and tasteless. It is dissolved 
by oil of turpentine, and some other oils, and more readily 
in sulphuret of carbon. Its vapor is soluble in vapor of alco- 
hol, but fluid alcohol does not dissolve solid sulphur. 

284. In its chemical relations it much resembles oxygen. 
It forms sulphurets with most of the elements that form 
oxyds, and these sulphurets often unite to form bodies 
analogous to salts, as the oxyds do. Berzelius with much 
reason argues that its binary combinations, from their analogy 
to the oxyds, should be called sulphids, and not sulphurets. 

Its uses are well known. It is one of the essential ingre- 
dients of gunpowder, and is the basis of all kinds of matches. 
Nearly all the sulphuric acid used in the arts is made from 
it. The gas arising from its combustion is employed in 
bleaching straw and woolen goods ; and in medicine it has a 
specific power in certain obstinate cutaneous diseases. 

Compounds of Sulphur with Oxygen. 

285. With oxygen it unites in several proportions. It 
burns in common air with a pale blue flame, and gives the 
well known odor of a burning match, forming only sulphurous 
acid, which is its lowest compound with oxygen. The com- 
pounds of sulphur and oxygen are numerous, but only two 
of them are of sufficient importance to engage our attention 
at present, viz : — 



Is it volatile ? Has it odor when cold ? How does it act as an 
electric ? In what is it soluble ? 284. What are its chemical 
relations ? Why is it associated with oxygen ? Name its uses 
285. What compounds does it form with oxygen ? 
17 






194 NON-METALLIC ELEMENTS. 

Combination by weight. 

Symbol. Sulphur. Oxygen. 

Sulphurous acid, SO2 16-09 16 

Sulphuric acid, S0 3 16-09 24 

286. (1.) Sulphurous acid, (S0 2 .) — This is the sole pro- 
duct of the combustion of sulphur in common air or pure 
oxygen gas. But for experiment it is prepared by the action 
of sulphuric acid (S0 3 ) with heat on copper clippings or 
mercury, in a glass retort. One equivalent of oxygen is 
retained by the metal, and the other two with the sulphur are 
given off as sulphurous acid. Sulphurous acid is one of the 
gases which must be collected over mercury, or by displace- 
ment of air in dry vessels. Its high specific gravity renders 
it easy to do the latter. 

287. Properties. — This is a colorless gas, having a density 
of 2-21 : 100 cubic inches of it weigh 68-69 grains. It has 
a very pungent, suffocating odor, quite insufferable, and it at 
once extinguishes flame. A lighted candle lowered into a 
jar containing it is extinguished, and the edges of the flame, 
as it expires, are tinged with green. A solution of blue 
litmus or blue cabbage turned into a jar of the gas is at first 
reddened by the acid, and then bleached. Water absorbs 
37 times its volume of sulphurous acid, forming a strongly 
acid fluid. Its avidity for moisture is so great that it forms 
an acid fog with the water in the atmosphere, and a bit of ice 
slipped under a jar of it on the mercurial cistern is instantly 
melted ; the water absorbs the gas, and the mercury rises to 
fill the jar. Its bleaching power is only temporary. Articles 
bleached by it after a time regain their previous color. 

288. Sulphurous acid is easily condensed by cold and 
pressure into a fluid having a specific gravity of 1*45, which 
becomes a crystalline, transparent, colorless solid at — 105°. 
The solid is heavier than the liquid, and sinks in it. 

By volume* sulphurous acid contains one volume of oxygen 
and ^ volume of sulphur vapor, (191,) condensed into one 
volume. Sulphurous acid forms a series of salts with bases, 
which are called sulphites. 



286. How is sulphurous acid formed? How is it collected? 
287. Give its properties. Does it support the combustion of a 
candle ? How does it affect vegetable colors ? Is it dissolved by 
water ? What of its avidity for moisture ? Does it bleach perma- 
nently ? 288. Does it become liquid ? At what temperature is it 
solid ! Give its composition by volume. 



SULPHUR. 



195 



289. (2.) Sulphuric acid, (S0 3 , HO.) — This acid is one 
of the most important compounds known ; its affinities are 
very powerful, and no class of bodies is better understood by 
chemists than the sulphates. In the arts great use is made 
of sulphuric acid, many millions of pounds of it being annually 
consumed in manufacturing nitric and muriatic acids, the sul- 
phate of copper, and alum, and in the processes of dyeing. 

It is not formed by the direct union of its elements, since 
we have seen that only sulphurous acid can result from the 
combustion of sulphur in air. Sulphurous acid must be 
oxydized to form sulphuric acid. 

290. This may be done by passing a mixture of sulphu- 
rous acid with common air over spongy platinum, heated to 
redness in a tube, when there will issue from the open end of 
the tube a mixture of sulphuric acid in vapor, with nitrogen 
from the air. In the arts, however, this process cannot be 
used ; but sulphuric acid is made on a large scale by bringing 
together sulphurous acid, (S0 2 ,) nitrous acid, (N0 4 ,) and 
water, (HO,) all in a state of vapor, in a large chamber or 
room, when sulphurous acid (S0 2 ) passes to a higher state 
of oxydation (S0 3 ) at the expense of one half the oxygen of 
the nitrous acid, (N0 4 ,) which thus becomes reduced to the 
state of the deutoxy d 
of nitrogen, (N0 2 .) 
The arrangement 
employed is repre- 
sented in the an- 
nexed figure. A A 
is a chamber fifty 
feet or more long, 
lined on all sides 
with sheet lead. A 
very large leaden 
tube (B) opening 
into one end of the 
chamber, communicates with a furnace. Its lower end 
rests in a gutter (o 6) of dilute acid, to prevent the effects of 




289. What is said of the importance of sulphuric acid ? What 
are its chief uses in the arts ? How is it formed t 290. How may 
sulphurous acid be oxydized ? How is it done in the arts ? Of 
what use are the nitric and nitrous acids, in this process ? Describe 
the arrangement of the leaden chamber. 



196 NON-METALLIC ELEMENTS. 

too much heat, and the escape of the vapors. The sulphur 
is intioduced by a door (c) to an iron pan, and a fire built 
beneath, (n.) The heat melts the sulphur, which burns in a 
current of air passing over it, and the sulphurous acid thus 
formed enters the chamber in company with air and the 
vapors of nitric acid set free from small iron pans standing 
over the sulphur, and containing the materials to evolve 
nitric acid, (sulphuric acid and saltpetre.) A small steam- 
boiler (e) furnishes a jet of steam (x) as required, and a 
quantity of water covers the floor, which is inclined so as to 
be deepest at h. A chimney with a valve or damper (p) 
allows the escape of spent and useless gases. Things being 
thus arranged, the chamber receives a constant supply of 
sulphurous acid, common air, nitric acid-vapor, and steam. 
These react on each other ; the nitric acid (N0 5 ) gives up a 
part of its oxygen to the sulphurous acid, forming nitrous 
acid, (N0 4 ,) and finally the deutoxyd of nitrogen, (N0 2 .) 
The last substance in contact with air gains another equiva- 
lent of oxygen, to form nitrous acid anew, which is again 
destined to be deoxydized by a fresh portion of sulphurous 
acid. In this way a small quantity of nitric acid can be 
made to oxydize an indefinite amount of sulphurous acid ; 
serving the purpose, as it were, of a carrier of oxygen from 
the atmospheric air to the sulphurous acid. Meanwhile the 
water on the floor of the chamber grows rapidly acid ; and 
when it has attained a specific gravity of about 1-5, it is 
drawn off and concentrated by boiling, first in open pans of 
lead until it becomes strong enough to corrode the lead, and 
afterwards in stills of platinum until it has a density of about 
1*8, in which state it is sold in carboys, or large bottles 
packed in boxes. 

291. The jwocess of forming sulphuric acid is easily 
illustrated in the class-room, by an arrangement of apparatus 
like that shown in the adjoining figure. Two flasks (a b) 
are so connected by bent tubes with a large bottle, that from 
one (a) sulphurous acid, and from the other (b) nitric oxyd 

What vapors enter the chamber ? What use is made of steam ? 
What receives and condenses the vapors ? Explain the successive 
changes which take place in the chamber. How can a small quan- 
tity of nitric acid answer the purpose ? How is the acid water 
from the chamber concentrated? 291. How can we illustrate this 
process in the class-room ? 



SULPHUR. 



197 



gases (304) are made to pass into the middle bottle, the inner 
surface of which is slightly moistened. By blowing in 
occasionally at c, the spent gases are ejected at d, and fresh 
air introduced. Under these circumstances the interior of 
the central vessel is soon 
covered with a white crys- 
talline solid, which appears 
to be a compound of sul- 
phurous acid and nitrous 
acid, (S0 2 ,N0 4 .) This 
substance is decomposed 
by a larger quantity of 
water into sulphuric acid 
and hyponitrous acid, and 
as it is known to be formed 
in the leaden chambers in 
large quantities, it is supposed to have an important influence 
in the production of sulphuric acid. 

292. Sulphuric acid unites with water in four proportions ; 
namely, 




Nordhausen acid, 
Oil of vitriol, 
Acid of sp. gr., 1*78, 
Acid of sp. gr., 1*63, 



2(S0 3 )HO 
S0 3 ,HO 
S0 3 ,HO + HO 
S0 3 ,HO + 2H 



293. The most concentrated sulphuric acid, however, is 
made by distilling dry sulphate of iron in earthenware 
retorts, at a red heat, when the acid of the salt with half an 
equivalent of water comes over in vapor, and is condensed 
in earthen tubes. It is a dark-brown, oily fluid, of the 
specific gravity of 1*9, or nearly twice as heavy as water, 
and with such an avidity for water as to hiss like hot iron 
when dropped into it. This sort of acid is made at Nord- 
hausen, in Saxony, and is commonly called the Nordhausen 
sulphuric acid. It has the composition" of 2S0 3 ,HO=89*19. 
When it is put in a retort and moderately heated, a white 
crystalline product is obtained from it, which is dry, or anhy- 



Explain the arrangement and reaction. What is the composition 
of the white crystalline compound ? How does water affect it ? 
292. What compounds does sulphuric acid form with water ? 293. 
How is the strongest sulphuric acid made ? What is its character ? 
Us strength ? its formula ? What is it called ? 

17* 



198 NON-METALLIC ELEMENTS. 

drous sulphuric acid, (S0 3 .) Common sulphuric acid, when 
as strong as possible, has still one equivalent of water, as 
above. It also unites with two equivalents, (S0 3 ,HO-fHO,) 
with a specific gravity of 1*780. When acid of this strength 
is exposed to a temperature of 32°, it freezes in large crys- 
tals. Great heat is generated from the mixture of strong 
sulphuric acid and water, and a diminution of bulk attends 
the mixture. When exposed to a temperature of 15°, sul- 
phuric acid freezes ; and at 620° it boils, giving off a dense 
white vapor. It is intensely acid to the taste, and deadly, 
if by any accident it is swallowed, corroding and burning the 
organs with intense heat. It blackens nearly all inorganic 
matters, charring or burning them like fire. Its strong dis- 
position for water enables us to employ it in desiccation, and 
in the absorption of aqueous vapor, (122.) 

294. The silky anhydrous compound (S0 3 ) obtained from 
the distillation of Nordhausen acid, (2S0 3 + HO,) does not 
possess acid properties when dry, but water at once changes 
it to common sulphuric acid. It has therefore been inferred 
that sulphuric acid cannot exist without water, or that water 
is essential to the acid property. In this case it is supposed 
that the oxygen of the water joins that already with the sul- 
phur, (forming S0 4 ,) while the new compound thus produced 
unites with hydrogen, forming S0 4 H. Some writers prefer 
to express the composition of sulphuric acid in this way, 
because it commits them to no theory, but is merely a state- 
ment of the number of atoms of each element in the com- 
pound, without attempting to decide how the elements may 
be united. 

295. Chlorid of sulphur is prepared by passing dry 
chlorine over melted sulphur. It is a volatile, deeply-colored 
liquid, of a disagreeable odor, boils at 280°, and has a density 
of 1*687. It consists of two equivalents of sulphur and one 
of chlorine, (S 2 C1.) It is decomposed by water. 

There are also bromids and iodids of sulphur, which how- 
ever possess very little interest. 



Give the composition of the common sulphuric acid. At what 
strength and temperature does it freeze ? When mingled with 
water, what happens ? Give other properties of sulphuric acid. 
294. Is the silky compound acid ? To what does the common acid 
owe its acid properties ? What view is given of the possible 
arrangement of its atoms ? 295. What compounds of sulphur are 
here named ? 



SELENIUM. 199 

7. SELENIUM. 

Equivalent, 39*57. Symbol, Se. Density, 4-3. 

296. History and Properties. — This element was dis- 
covered by Berzelius in 1818, and named by him from 
selene, the moon. It is associated in nature with sulphur in 
some kinds of iron pyrites, and also at the Lipari Islands 
combined with sulphur and accompanied by other volcanic 
products. 

It closely resembles sulphur in most of its properties, as 
well as in its natural associations. At common temperatures 
it is a brittle solid, opake, and having a metallic lustre like 
lead, but in powder it is of a deep red color. Its specific 
gravity is between 4-3 and 4*32. It softens at 212°, and 
may then be drawn out into red colored threads ; at a little 
higher temperature it melts completely, and boils at 650°, 
giving a deep yellow vapor without odor. It is insoluble. 
When heated in the air, it combines with oxygen and gives 
out a disagreeable and strong odor, like putrid horse-radish. 
Before the blowpipe, on charcoal, it burns with a pale blue 
flame, and -^ of a grain, so heated, will fill a large apart- 
ment with its odor. It is a non-conductor of heat and of 
electricity. 

297. The compounds of selenium with oxygen are three, 
two of which are acids analogous to sulphurous and sulphu- 
ric acids. Their composition is, 

Composition by weight. 





Symbol. 


Selenium. 


Oxvgen. 


Oxyd of selenium, 


SeO 


39-57 


8 


Selenious acid, 


Se0 2 


39-57 


16 


Selenic acid, 


Se0 3 


39.57 


24 



298. Oxyd of selenium is formed when selenium is 
heated in the air. It is a colorless gas, and possesses the 
strong odor before mentioned. Selenious acid is a white 
and very soluble body, procured by the action of nitric acid 
on selenium. It is distinctly acid, and can be sublimed 



296. When, where,, and by whom was selenium discovered ? 
Give its properties. What physical property most distinguishes it ? 
297. What are its compounds with oxygen ? 298. Characterize 
these compounds. (1.) The oxyd; (2.) Selenious acid. 



200 NON-METALLIC ELEMENTS. 

without change of properties. Selenic acid is formed by 
oxydizing selenium with nitrate of potash, and it may also be 
formed by the action of nitric acid on selenium. It strongly 
resembles sulphuric acid in its acid properties and compounds. 
Both selenious and selenic acids form salts with the alkalies 
and bases, every way similar to the sulphites and sulphates. 

With sulphur, selenium forms a sulphuret which is found 
native among volcanic products. 

8. TELLURIUM. 

Equivalent, 64*14. Symbol, Te. 

299. Tellurium is a very rare substance, more analogous 
to sulphur in its chemical relations than to the metals, with 
which it is usually classed. It is found native or alloyed 
with gold, and is also combined with bismuth, silver, &c, in 
several very rare minerals, as telluric bismuth, graphic 
tellurium, and aurotellurite. 

When pure, it is a tin-white, brittle substance, with a 
metallic lustre, and a density of 6*26. It melts at low red- 
ness, is very volatile, and is a bad conductor of heat and 
electricity. It burns when strongly heated in the air, and 
forms tellurous acid, Te0 2 . Telluric acid, (Te0 3 ) can also 
be formed from tellurous acid, by a process which need not 
now be described. 

CLASS IV. 

9. NITROGEN, OR AZOTE.* 

Equivalent, 14-06. Symbol, N. Density, -972. 

300. Preparation and History. — This gas forms four- 
fifths of the air we breathe, and is an essential constituent of 
most organic substances. It enters into a great variety of 
combinations. 

(3.) Selenic acid. 299. What is tellurium ? Give its properties. 
What acids does it form ? 300. Give the symbol and equivalent of 
nitrogen. 



• 



* So called from a, privative, and zoe, life, from its deadly effects. 
Nitrogen is from nitrum, nitre, and gannao, I form. 



NITROGEN. 



201 




It is most easily procured for purposes of experiment from 
the atmosphere, by withdrawing the oxygen of the air by 
phosphorus. This is easily done 
by burning some phosphorus in a 
floating capsule, in an air-jar over 
the pneumatic cistern. The strong 
affinity of phosphorus for oxygen 
enables it to withdraw every 
trace of this element, leaving be- 
hind nitrogen nearly pure, con- 
taining about ■£$ of phosphorus 
and the vapors of phosphorus, 
with the snow-white phosphoric 
acid which the water soon absorbs. The first combustion of 
the phosphorus expels a portion of the air by expansion ; but 
as the combustion proceeds the water rises in the jar, 
showing a considerable absorption. Pure nitrogen is also 
easily obtained from fused nitrate of ammonia by aid of a 
bit of zinc, which is lowered by a wire passing through the 
cork of the tubulure, so as to bring the zinc into contact with 
the fused salt. As soon as the protoxyd of nitrogen begins to 
be set free, oxyd of zinc is formed, and nitrogen evolved, 
NO-fZn=ZnO-f-N. Other processes may be used, such 
as passing air over cuttings of copper in a tube heated to 
redness, and the action of nitric acid on lean animal muscle ; 
but the method first named will best suit our purposes. 

301. Properties of Nitrogen. — Nitrogen is best described 
by saying that its properties are entirely negative. It is a 
fixed gas, which no degree of cold and pressure has ever 
liquefied. It cannot support combustion, nor life ; yet it is 
not poisonous, and kills merely by exclusion of air. It has 
neither taste nor smell. It is a little lighter than air, having 
a density of *972. It does not combine directly with any 
element, although by indirect, methods it enters into powerful 
combinations with several. In the air, it seems to act the 
part of a diluent, and is not, properly speaking, in chemical 
combination with the oxygen there present ; the atmosphere 
is regarded as a mixture of the two gases, diffused through 
each other, (132.) 



How is it prepared? 301. What are its properties? Does it 
support life and combustion ? Is it poisonous ? Does it directly 
combine with other elements ? How does it act in common air ? 



202 NON-METALLIC ELEMENTS. 



1. The Chemical History of the Atmosphere. 

302. We have already (24) given a sufficient account of 
the mechanical or physical properties of the atmosphere and 
the laws of gases, and need not repeat them here. The 
number and proportion of the constituents of the atmosphere 
are constant, although their union is only mechanical. 
Repeated analyses have shown that atmospheric air is 
always formed of nitrogen, oxygen, watery vapor, a little 
carbonic acid, traces, perhaps, of carbureted hydrogen, and 
a small quantity of ammonia. The air on Mount Blanc, or 
that taken in a balloon by Gay Lussac from 21,735 feet 
above the earth, has the same chemical composition as that 
on the surface, or at the bottom of the deepest mines. The 
carbonic acid being liable to changes in quantity from local 
causes, is found to vary slightly. To the constituents 
already named, we may add the aroma of flowers and other 
volatile odors, and those unknown mysterious agencies which 
affect health, and are called miasmata. We may state the 
composition of the atmosphere in 100 parts, to be — 

By weight. By measure. 

Nitrogen, 77 parts. 79*19 

Oxygen, 23 20-81 



100 100-00 « 

To this we must add from 3 to 5 measures of carbonic 
acid in 10,000 of air; a variable quantity of aqueous vapor, 
and a trace of ammonia. Nitric acid has also been some- 
times found in small quantity in rain-water, formed in the 
air by the electrical discharges of thunder-clouds, and washed 
out by the rains. 100 cubic inches of dry air weigh 31-011 
grains. 

303. Analysis of Air. — The oxygen of the air is ab- 
stracted by all substances having an affinity for it, with the 
same ease as if nitrogen were not present. The experiments 
described in 300 are one mode of analyzing air. The term 



302. Describe the chemical composition and properties of the air. 
Do the proportions vary ? Which constituents may vary ? Give 
its constitution by weight and measure. How much carbonic acid 
is there in it ? What do 100 cubic inches weigh ? 303. How is the 
air analyzed ? 




NITROGEN. 203 

audiometry has been applied to processes for determining the 
purity of the air, from words signifying " a 
good condition of the air." One of the sim- 
plest means of analyzing the atmosphere, 
consists in removing the oxygen by the slow 
combustion of phosphorus. For this purpose 
the arrangement is made, as in the annexed 
figure, by sustaining a stick of phosphorus on 
a wire in a confined portion of air, contained 
in a graduated glass tube, whose open end is 
beneath water. A gradual absorption takes 
place, and in about twenty-four hours the 
water ceases to rise in the tube, by 
which we know that the phosphorus 
has removed all the oxygen. The 
water absorbs the resulting phosphorous acid, and 
we may read off, by the graduation on trT§- tube, 
the amount of gas removed. A narrow-necked 
bolt-head shows this result in a more striking 
manner in the class-room, the large volume of air 
in the ball causing a very appreciable rise of water 
in the stem during the course of a lecture. When 
speaking of hydrogen, we will mention another 
method of eudiometry. The agency of the air in 
combustion and respiration will also be explained 
under the appropriate heads. From this mechanical mixture 
of oxygen and nitrogen, we pass to the 

2. Compounds of Oxygen and Nitrogen. 

304. Nitrogen unites with Oxygen, forming five com- 
pounds, three of which are acids. Their names and con- 
stitution are thus expressed : 



Protoxyd of nitrogen, (nitrous oxyd,) 
Deutoxyd of nitrogen, (nitric oxyd,) 
Hyponitrous acid, 
Nitrous acid, 
Nitric acid, 



What is eudiometry ? Give a simple mode of illustrating the 
analysis of air. 304. Name the compounds of oxygen with nitrogen. 
Give their composition on the black-board. 






Combination 


by weight. 


Symbol. 

NO 


Nitrogen. 
14-06 


Oxygen. 
8 


N0 2 


14-06 


16 


N0 3 


14-06 


24 


N0 4 


14-06 


32 


N0 5 


14-06 


40 



204 NON-METALLIC ELEMNETS. 

This group of compounds is generally considered as one 
of the most instructive examples of the law of multiple pro- 
portions (184) in the whole range of chemical affinities, and 
our attention is arrested by the fact, that the same elements 
which form our salubrious air, should, by mere change of 
proportions, unite to form the corrosive and deadly acids of 
nitrogen. 

305. Protoxyd of Nitrogen, (NO,) Nitrous Oxyd, or 
Laughing Gas. — This gaseous compound of nitrogen is best 

prepared by heating nitrate of ammonia 
(NH 3 , N0 5 ) in a glass flask by the 
aid of a spirit-lamp. The arrangement 
is here shown ; the gas is given off at 
about 400° to 500°, and is delivered 
by the bent tube to an air-jar on the 
pneumatic trough. The nitrate of 
ammonia^which is a crystalline white 
salt formed by neuralizing dilute 
nitric acid by carbonate of ammonia, 
is so constituted as to be resolved by 
heat alone, into nitrous oxyd and 
water; thus, NH 4 0, N0 3 , become by 
heat 4HO + 2NO. The hydrogen in 
the ammonia takes so much oxygen 
from the nitric acid — three equivalents — as is required to 
form three equivalents of water, and the nitrogen, both of 
the acid and ammonia, unites with the remaining oxygen to 
form the gas in question. Consequently the equivalents of 
these elements show us that 71 grains of nitrate of ammonia 
will yield 44 grains of nitrous oxyd and 27 grains of water. 
Care must be taken not to heat this salt too highly, as it then 
yields nitric oxyd and nitrous acid fumes. If a red cloud 
towards the close of the operation is seen to rise, the heat 
must be abated. 

306. Properties. — Nitrous oxyd is a colorless gas, with 
a faint, agreeable odor, and a sweetish taste. With a pres- 
sure of fifty atmospheres at 45° F. it becomes a clear liquid, 
and at about 150° below zero freezes into a beautiful, clear, 
crystalline solid. By the evaporation of this solid, a degree 



305. How is protoxyd of nitrogen prepared ? What caution is 
needed ? 306. What are the properties of this gas ? Has it been 
solidified, and at what temperature ? 




NITROGEN. 205 

of cold may be produced far below that of the carbonic 
acid bath (137) in vacuo, (or lower than — 174°F.) It evap- 
orates slowly, and does not freeze, like carbonic acid, by 
its own evaporation. The specific gravity of nitrous oxyd 
is 1-525; 100 cubic inches of it weigh 47*29 grains. Cold 
water absorbs about its own volume of this gas. It cannot, 
therefore, be long kept over water, but may be collected in 
vessels filled with warm water over the water-trough. It 
supports the combustion of a candle, and sometimes re-lights 
its red wick with almost the same promptness as pure 
oxygen. Phosphorus burns in it with great splendor. With 
an equal bulk of hydrogen, it forms a mixure that explodes 
with violence by the electric spark or a match ; the residue 
is pure nitrogen, the oxygen forming water with the hydro- 
gen. 

307. Its most remarkable property, and that from which 
it derives the name of ' laughing gas, 1 is its intoxicating 
power on the system. For this purpose it is breathed when 
pure or diluted with air, through a wide tube, connected with 
a silk or elastic-gum bag or with a gas-holder, and may be 
inhaled and exhaled several times, until giddiness comes on, 
and a feeling of joyous or boisterous exhilaration. This is 
shown by a disposition to laughter, a flow of vivid ideas and 
poetic imagery, and often by a strong disposition to muscular 
exertion. These sensations are usually quite transient, and 
pass away without any resulting languor or depression. In 
a few cases dangerous consequences have followed its use, and 
it should be employed with great caution. In at least one 
case,* at Yale College, it produced a permanent restoration of 
health and joyous exhilaration of spirits which continued for 
months. Its effects, however, in different individuals are 
various. 

308. Deutoxyd or Binoxyd of Nitrogen, Nitric Oxyd. — 
This gas is easily prepared by adding strong nitric acid to 



How does the solid gas behave ? Is this an absorbable gas ? 307. 
What is its most remarkable property ? How does it affect the sys- 
tem ? Are its effects uniform ? 308. How is binoxyd of nitrogen 
formed ? 



* In another case consumptive symptoms resulted, which continued 
for years, although not eventually fatal. 
18 




206 NON-METALLIC ELEMENTS. 

clippings of sheet copper, contained in a 
bottle arranged with two tubes like the 
annexed figure ; a little water is first put 
with the copper cuttings, and the nitric 
acid poured in at the tall funnel tube 
until brisk effervescence comes on. In 
this case the copper is oxydized by a part 
of the oxygen of the acid, and the oxyd 
thus formed is dissolved by another por- 
tion of acid. The nitrogen in union with 
the two equivalents of oxygen is given off 
as nitric oxyd, which, not being absorbed 
by water, may be collected over the pneu- 
matic-trough. Many other metals have the same action with 
nitric acid. 

309. Properties. — Nitric oxyd is a transparent, colorless 
gas, tasteless and inodorous, but excites a violent spasm in 
the throat when an attempt is made to breathe it. It has 
never been condensed into a liquid. Its specific gravity is 
1*039, and 100 cubic inches weigh 32-22 grains. It contains 
equal measures of oxygen and nitrogen uncondensed. 

A lighted taper is instantly extinguished when immersed 
in it, but phosphorus previously well inflamed will burn in it 
with great splendor. When this gas comes into contact with 
the air, deep red fumes are produced, by its union with the 
oxygen of the air to form nitrous acid. If to a tall jar, nearly 
filled with nitric oxyd, standing over the well of the cistern, 
pure oxygen gas be turned up, deep blood-red fumes instantly 
fill the vessel, much heat is generated, and a rapid absorption 
results from the solution of the red nitrous acid vapors in the 
water of the cistern. If both gases are pure and in the right 
proportions, the absorption will be complete, and no gas left 
in the vessel. If purple cabbage-water, made green by an 
alkali, is used to fill the air-jar, the acid formed at once turns 
the vegetable infusion to a lively red. 

310. Hyponitrous Acid, (N0 3 .) — This is a thin mobile 
liquid, formed from the mixture of four measures of deut- 
oxyd of nitrogen with one measure of oxygen, both perfectly 



309. What are its properties ? Is it respirable ? Is it condensa- 
ble ? Give its specific gravity and its composition by volume. Does 
it support combustion ? What is its action with oxygen ? What fine 
experiment is named ? 310. What is hyponitrous acid ? 



NITROGEN. 



207 



dry, and exposed after mixture to a temperature below zero 
of Fahrenheit. It has an orange red vapor, and at common 
temperatures is green, but at zero is colorless. Water decom- 
poses it, forming nitric acid and deutoxyd of nitrogen. Its 
most interesting compound is that formed with sulphurous 
acid in the manufacture of sulphuric acid, (290,) as already 
described. 

311. Nitrous Acid, (N0 4 .) — We have already anticipated 
the mode of forming this compound and its properties in de- 
scribing the deutoxyd of nitrogen. Whenever the latter body 
is brought into contact with the air, red nitrous acid fumes are 
formed. By decomposing the nitrate of lead in an earthen 
retort nitrous acid and oxygen are obtained and the former 
may be condensed in a very cold receiver. Jn this state it is 
a nearly colorless fluid, which becomes yellow and finally red 
as the temperature rises. It boils at 82°, and is decomposed 
by water, nitric acid and deutoxyd of nitrogen being formed. 

This body, although considered as an acid, is not very 
well characterized. The red color of the strong, fuming 
nitric acid of commerce, is due to the presence of nitrous 
acid dissolved in the fluid. 

312. Nitric Acid, Aqua Fortis, (N0 6 HO.)— This powerful 
and important acid is bet- 
ter known than any other r 
of the compounds of nitro- 
gen. It is best obtained 
by decomposing either the 
nitrate of soda or of pot- 
ash, (saltpetre,) by strong 
sulphuric acid. The ar- 
rangement of apparatus 
required is seen in the 
adjoining cut. The re- 
tort ( R ) contains the 
nitre in small crystals, 
and should be supported 
in a sand-bath ; or if the 
salt does not exceed a pound 
or two, a naked fire an- 

What compound of it have we already described? 311. What is 
said of nitrous acid ? How can it be obtained ? Can it be mixed with 
water ? 312. How is nitric acid formed ? Describe the arrangement 
of apparatus and the proportions of the materials. 




208 NON-METALLIC ELEMENTS. 

swers very well. To it is added about twice its weight of strong 
oil of vitriol. The sulphuric acid takes the place of the nitric, 
forming bisulphate of soda or potash, and the strong nitric acid 
distils over to the receiver, which is kept cool by water or ice. 
No luting of any kind must be employed about its neck. The 
retort becomes very hot, and the whole operation is a critical 
one. The dense red vapors of nitrous acid which appear in 
the early stage of the process disappear entirely after a time, 
and are again renewed toward its close. When the deep 
blood-red vapors prevail, and but little acid condenses in the 
neck of the retort, the heat is remitted and the receiver dis- 
connected ; the bisulphate of potash is then in a state of 
quiet fusion and intensely hot, (about 600° F.) When 
nearly cold it may be gradually dissolved by hot water, but 
the retort is generally sacrificed in the operation. The 
strongest nitric acid is produced only when equal weights of 
sulphuric acid and nitre are used. 

313. Properties. — Nitric acid thus obtained is a highly 
colored, red, fuming, and very corrosive acid, of great 
energy. The color is due to nitrous and hyponitrous acid, 
the pure nitric acid being colorless, with a specific gravity 
of 1*5, and boiling at 248°. It stains the skin yellow, and 
acts violently on most organic matters and metals. Poured 
on powdered recently ignited charcoal, deflagration speedily 
ensues, and warm oil of turpentine is at once inflamed by it. 

314. One equivalent of water is essential to the character 
of nitric acid, (N0 5 , HO,) the simple N0 5 being an unknown 
substance. The strongest nitric acid has nine parts of water 
to 54 of real acid. Like sulphuric acid, it has several 
definite combinations with water, which freeze and boil at 
very different temperatures. Strong aqua fortis freezes at 
about 50° below zero, but when diluted with one-half water 
it freezes at — 1|°. The green hydrated nitrous acid freezes 
into a bluish white solid. 

315. It oxydizes other substances very powerfully, from 
the great amount of oxygen it contains. It is the usual 



What changes are noticed as the process goes on ? When is the 
process arrested ? 313. What are its properties ? What gives it its 
ordinary color ? How does it effect the skin, the metals and char- 
coal ? 314. Is the anhydrous nitric acid known ? What is the com- 
position of the strongest nitric acid ? Is it ever frozen, and at what 
temperature ? 315. How does it affect other bodies ? 



PHOSPHORUS. 209 

solvent of most of the metals, when we would carry them to 
the condition of peroxyds. In all such cases, the binoxyd 
of nitrogen is formed, (N0 2 ,) which at once produces red 
fumes in the air. It forms a large class of salts, (nitrates,) 
all of which are soluble in water. This makes it difficult 
to detect the presence of this acid. It however decolorizes 
a solution of indigo in sulphuric acid, which is the common 
test for the presence of nitric acid ; and with a drop or two 
of hydrochloric acid it dissolves gold leaf. 

10. PHOSPHORUS. 

Equivalent, 31-38. Symbol, P. Density, 1-77. 

316. History. — Phosphorus is an element nowhere seen 
free in nature, but it exists largely in the animal kingdom, 
combined with lime, forming bones, and it is found also in 
other parts of the body. In the mineral kingdom it exists in 
several well known forms, particularly in the mineral called 
apatite, which is a phosphate of lime. It is introduced into 
the animal system by the plants used as food, whose ashes 
contain a notable quantity of phosphate of lime. It was dis- 
covered in 1669 by Brandt, an alchemist of Hamburg, while 
engaged in seeking for the philosopher's stone, in human 
urine. Its name implies its most remarkable property, (phos, 
light, and phero, I carry.) 

317. Preparation. — Phosphorus is now procured in im- 
mense quantities from burnt bones, for the manufacture of 
friction matches. The bones are calcined until they are quite 
white ; they are then ground to a fine powder, and fifteen 
parts of this are treated with thirty parts of water and ten of 
sulphuric acid : this mixture is allowed to stand a day or two, 
and is then filtered, to free it from the insoluble sulphate of 
lime, formed by the action of the oil of vitriol on the bones. 
The clear liquid (which is a soluble salt of lime and phos- 
phoric acid) is then evaporated to a syrup, and a quantity of 
powdered charcoal added. The whole is then completely 
dried in an iron vessel and gently ignited. After this, it is 
introduced into a stoneware or iron retort, to which a wide 
tube of copper is fitted, communicating with a bottle in which 

316. What is phosphorus ? When and by whom discovered ? 
What existence has it in nature? 317. How is it prepared? De- 
scribe the process of procuring it. 
18* 



210 



NON-METALLIC ELEMENTS. 




is a little water, that just covers the open end of the tube ; a 

small tube carries the gases given out to a chimney or vent. 

The retort being very gradually heated, the charcoal decom- 
poses the phosphoric acid, carbonic 
acid and carbonic oxyd gases are 
evolved, and free phosphorus flows 
down the tube into the bottle, where it 
is condensed. The operation is a criti- 
cal one, and often fails from the break- 
ing of the retort. Splendid flashes of 
light are constantly given out during 
the operation, from the escape of phos- 
phureted hydrogen. The crude phos- 
phorus thus obtained is purified by 
melting under water, and it is then cast 
into glass tubes, where it is allowed to 

cool, forming the sticks in which it is sold. 

318. Pure phosphorus is a yellowish semi-transparent 
solid, which cuts like wax, is brittle at 32°, and then shows a 
crystalline fracture. It has a density of 1*77. It is insolu- 
ble in water, but dissolves in several oils, in ether, alcohol, 
and in sulphuret of carbon : from the last it crystallizes in 
regular dodecahedrons, (220.) It melts at 108° into a color- 
less liquid, and boils at 550°, forming a colorless vapor of a 
density of 4*327. 

319. Phosphorus is exceedingly inflammable, being easily 
set on fire by the heat of the hand, and great caution is re- 
quired in managing it. It must be kept under water, to which 
alcohol enough may be added to prevent its freezing in winter. 
If exposed to the air, it wastes slowly away, forming phos- 
phorous acid, and in the dark it is seen to be luminous. The 
vapor which then comes from it, has a strong garlic odor, 
which does not belong either to the pure phosphorus or its 
acid compounds. A little defiant gas, the vapor of ether, or 
any essential oil, will entirely arrest the slow oxydation of 
phosphorus in air. The presence of nitrogen or hydrogen 
seems to be essential to this operation, as in pure oxygen, 
phosphorus does not form phosphorous acid at common tern 



318. What is its usual condition ? In what is it soluble ? How is 
its density when solid and in vapor ? 319. "What of its inflamma- 
bility ? How is it kept ? How does air affect it ? What substances 
arrest its slow combustion ? How does it burn in oxygen ? 



Symbol. 


Phosphorus. 


Oxygen. 


P 2 


62-76 


8 


PO 


31-38 


8 


P0 3 


31-38 


24 


P0 5 


31-38 


40 



phosphorus. 211 

peratures. It burns in pure oxygen gas with great splendor, 
forming one of the most brilliant experiments in chemistry. 
For this purpose it is suspended in a metallic spoon, in a dry 
globe, filled with oxygen by displacement of air, as already 
described. 

1. Compounds of Phosphorus with Oxygen. 

320. The compounds of phosphorus with oxygen are four 
in number, and may be understood from the following list. 

Composition by Weight. 

Svmbol. 
Oxyd of phosphorus, 
Hypophosphorous acid. 
Phosphorous acid, 
Phosphoric acid, 

321. Oxyd of phosphorus is formed when a stream of 
oxygen gas is allowed to flovf from a tube upon phosphorus 
under warm water. The phosphorus burns under water and 
forms a brick-red powder, which is the oxyd in question, with 
much unburnt phosphorus. This oxyd is also formed when 
phosphorus is kept for a long time under water ; the sticks 
then become coated with the red oxyd. By heat, this oxyd 
is decomposed into phosphorous and phosphoric acids. 

322. Hypophosphorous acid is very little known, and we 
need not describe its mode of formation. Its salts are all sol- 
uble in water, and it is a powerful deoxydizing agent. 

323. Phosphorous Acid. — When some sticks of phospho- 
rus are placed in a funnel, and its mouth covered, a delicate 
stream of white vapor is seen to descend from the lower end 
of the tube, which may be collected in a tall foot-glass. 
These vapors are phosphorous acid, formed from the slow 
combustion of the phosphorus by the oxygen of the air. It 
is also formed when phosphorus is burnt in a very limited 
supply of oxygen gas. In both cases it soon takes another 
dose of oxygen from the air, and becomes a mixture of phos- 
phorous and phosphoric acids. 

When first made, phosphorous acid is a dry white powder, 
having a very strong affinity for water, which it absorbs togethei 

320. Name the compounds of phosphorus with oxygen, and give the 
formulas? 321. Describe the oxyd, its formation and properties. 
How does heat affect it ? 322. What of hypophosphorous acid ? 323. 
How is phosphorous acid formed ? What are its properties ? 



212 NON-METALLIC ELEMENTS. 

with oxygen from the air, and gradually becomes phosphoric 
acid. Its solution is sour, and it forms well determined salts, 
(phosphites.) 

324. Phosphoric acid is formed when phosphorus is 
burned in a copious supply of dry air, as in the experiment 
for obtaining nitrogen, (300,) or that of phosphorus in dry 
oxygen, (319.) When wanted in large quantity, it is prepared 
from the ashes of bones treated with sulphuric acid, as already 
described. This solution is first freed from lime and magne- 
sia, and is then evaporated to dryness and ignited, when the 
sulphuric acid is driven off and phosphoric acid remains 
behind melted, and solidifies on cooling into a colorless glass, 
which is then called glacial phosphoric acid. Phosphoric 
acid is also formed by the action of very strong nitric acid on 
phosphorus ; but the operation is a dangerous one, and should 
be attempted only on very small quantities of phosphorus, and 
with extreme caution. 

325. Phosphoric acid is a powerful acid, having an in- 
tensely sour taste, and all the attributes belonging to an acid. 
It has, when dry, a very strong affinity for water, and unites 
with it almost explosively, forming, according to circum- 
stances, three distinct compounds, or phosphates of water, 
whose constitution is as follows : 

Monobasic phosphate of water, or metaphosphoric acid, HO -f- P0 6 . 
Bibasic phosphate of water, or pyrophosphoric acid, 2HO4-PO5. 
Tribasic phosphate of water, or common phosphoric acid, 3HO -|- P0 6 . 

Each of these three phosphates of water is the source of 
a distinct series of salts with bases. The class of salts most 
generally known is that formed from the last phosphate of 
water, or the tribasic phosphates. The reader can consult 
Dr. Graham's Elements of Chemistry for a fuller account of 
this subject, which our limits prevent our giving in more 
detail. 

2. Compounds of Phosphorus, with Members of the 
II. Class. 

326. (1.) Chlorids of Phosphorus. — Of these there are 
two, the perchlorid, (PCI 5 ,) and sesquichlorid, (PC1 3 .) The 



324. How is phosphoric acid formed ? How from bones ? 325. 
Describe its properties. How does water affect it ? Give its com- 
pounds with water. Which is common phosphoric acid ? 



PHOSPHORUS. 213 

first is formed when phosphorus is introduced <into a jar of 
dry chlorine, where it inflames and lines the sides of the 
vessel with a white matter, which is the perchlorid of phos- 
phorus. This compound is very unstable, and when put in 
water both it and the water suffer decomposition, and hydro- 
chloric and phosphoric acids result. 

327. (2.) Bromids of Phosphorus. — Two of these com- 
pounds are also known, and are easily formed by mingling 
small quantities of the elements in a flask filled with dry 
carbonic acid gas ; they immediately react on each other, 
evolving heat and light, and form the protobromid of phospho- 
rus, (PBr 3 ,) which is a brown fluid, easily decomposed by 
water ; and the perbomid of phosphorus, (PBr 5 ,) which is 
a volatile yellowish white solid, that sublimes on the sides 
of the flask and is easily fused by gentle heat into a red 
fluid. It is decomposed by water into phosphoric and 
hydrobromic acids. 

328. (3.) Iodids of Phosphorus. — These elements com- 
bine in three proportions, forming protiodid of phosphorus, 
(PI,) sesquiodid of phosphorus (PI 3 ,) and the periodid of 
phosphorus, (PI 5 .) The union of these elements is accom- 
plished with energy by simple contact in a dry state. Their 
compounds are not important. 

329. (4.) Sulphuret of Phosphorus. — Sulphur unites 
with phosphorus with prodigious violence, frequently with 
a dangerous explosion, and more than 30 or 40 grains of the 
latter cannot be safely put with the sulphur. Seleniuret of 
phosphorus is formed in the same manner as the last, and is 
similar to it in all its properties. 



CLASS V. THE CARBON GROUP. 

11. CARBON. 

Equivalent, 6. Symbol, C. Specif c gravity in vapor, 0*421. 
Solid in the diamond, 3-52. 

330. History. — Charcoal and mineral coal, which are 
the two common forms of carbon, have been known from 



326. Name the chlorids of phosphorus. 327. How many bromids 
of phosphorus are there ? How are they formed ? 328. How many 
iodids of phosphorus, and how formed ? 329. What is said of the 
union of sulphur and phosphorus ? What of its seleniuret ? 



214. 



NON-METALLIC ELEMENTS. 



the remotest times of history. Its great importance in the 
daily wants of society, makes it one of the most interesting 
of the elementary bodies, and our interest in it is not dimin- 
ished from the fact that the charcoal and mineral coal which 
we use as fuel, and the black lead of our pencils, are 
essentially the same thing with that rare and costly gem, the 
diamond. The three distinct and very dissimilar forms of 
existence which this element assumes, give us one of the 
best examples known of the allotropism (264) of bodies. We 
will very briefly mention the principal characters of the three 
forms of carbon — (1,) the diamond, (2,) graphite or plumbago, 
(4,) mineral coal and charcoal. 

331. The diamond is pure carbon crystallized. It takes 
the forms of the regular system, or first crystalline class, 
(220,) of which the annexed figures are some of its common 
modifications. Its crystalline faces are often curved, as in 




the second figure. The diamond is the hardest of all known 
substances, and can be scratched or cut only by its own dust. 
The solid angles of this mineral, formed by the union of curved 
planes, are much used, when properly set, for cutting glass, 
which is done with great ease and precision. It has a specific 
gravity of 3*52, and the highest value of any kind of treasure. 
The most esteemed diamonds are colorless, and of an inde- 
scribable brilliancy ; this gem has also a peculiar lustre known 
as the ' adamantine lustre.' They are oftenslightly colpred, 
of a yellowish, rose, blue, or green, and even black tint. 
The largest known diamond belongs to the Great Mogul, and 
when found weighed 2769-3 grains, or nearly six ounces : it 
has the form and size of half a hen's egg. The most highly 
valued diamond in the world is called the Pitt diamond, and 
was sold to the Duke of Orleans for £130,000. It weighs less 
than an ounce. This was the gem which Napoleon mounted in 



330. Give the equivalent and density of carbon. What is here 
said of carbon ? What three forms of carbon are named ? 331. What 
is the diamond? What forms does it occur under? Describe it as 
noticed in the text. What is the native source of the diamond? 



CARBON. 215 

the hilt of his Sword of State. The diamond is usually found 
in the loose sands of rivers, and is generally accompanied by 
gold and platinum. Its native rock is supposed to be a pecu- 
liar flexible kind of sandstone, called itacolumite ; and it 
is sometimes found loosely imbedded in a ferruginous conglo- 
merate in Brazil. A few diamonds have been found in the 
United States. 

332. From its high refractive power (56) the diamond is 
supposed to be of vegetable origin. The sun's light seems 
to be absorbed by the diamond, for it phosphoresces most 
beautifully for some time in a dark place, after it has been 
exposed to the sun. It is a non-conductor of heat and elec- 
tricity, and is very unalterable by any chemical means. It 
is infusible, and not attacked by acids or alkalies. But 
heated to redness in the air, it is totally consumed, and the 
sole product of its combustion is carbonic acid gas, which 
alone is sufficient proof that diamond is pure carbon. 

333. (2.) Graphite or Plumbago. — This form of carbon 
is sometimes improperly called " black lead," but it does not 
contain a trace of lead in its composition, and bears no re- 
semblance to it, except that both have been used to mark 
upon paper. 

This peculiar mineral is found in the most ancient rocks, 
as well as with those of a more modern era. It is also fre- 
quently found in company with coal, and is sometimes formed 
artificially, as in the fusion of cast iron. It almost always 
contains a trace, and sometimes several per cent, of iron, 
which is however foreign to it ; otherwise it is pure carbon. 
It is very much used for making pencils, and the coarser 
sorts are manufactured into verjr useful and refractory melt- 
ing pots. The most valued plumbago for the finest drawing 
pencils, has been brought chiefly from the Borrowdale mine 
in Cumberland, England ; but it is a common mineral in this 
country, as, for instance, at Sturbridge in Massachusetts, and 
many other places. It is sometimes found crystallized in flat 
six-sided prisms, a form altogether incompatible with that of 
the diamond. It is soft, flexible, and easily cut ; feels greasy 

332. What origin has the diamond been supposed to have, and 
why ? What are its relations to heat, light, and electricity ? How 
affected by chemical means ? What does affect it ? 333. What is 
plumbago ? How found ? What use is made of it ? How does it 
crystallize ? What are its physical properties ? How does intense 
heat affect it ? 



J 



£16 NON-METALLIC ELEMENTS. 

and marks paper. It is quite incombustible by all ordinary- 
means, but burns in oxygen gas, forming only carbonic acid 
gas, and leaving a red ash of oxyd of iron. 

334. (3.) Coal. — The vast beds of mineral carbon, 
known to us as anthracite, bituminous coal, brown coal, 
and lignite, are all of them nearly pure carbon. Of the first 
two of these, no country has such abundant and excellent 
supplies as the United States. These accumulations of 
fuel are the remains of the ancient vegetation of the planet, 
which, long anterior to the creation of man, a bountiful Pro- 
vidence laid away in the bowels of the earth for his future 
use. Bituminous coal differs from anthracite only in having 
a quantity of bituminous matter united with it, which in the 
anthracite has been driven off by heat and pressure. 

335. Charcoal from wood is the carbonized skeleton of 
the woody fibre which is found in all plants. The best 
charcoal is made by heating sticks of wood in tight iron 
vessels, without contact of air, until all gases and vapors 
cease to be given off. A great quantity of acetic acid, tar, 
and oily matters, with water, are given out, and a jetty black, 
brittle, hard charcoal is left behind, which is a perfect copy 
of the form of the original wood. It is a non-conductor of 
heat, but conducts electricity almost as well as a metal. It 
is a very unchangeable substance, insoluble in water, acids, 
or alkalies, suffers little change from long exposure to air 
and moisture, and does not yield to the most intense heat to 
which it can be subjected. 

336. Charcoal has the property of absorbing gases to a 
most remarkable degree, at common temperatures. A frag- 
ment of recently heated charcoal, of a convenient size to be 
introduced under a small air-jar over the mercurial cistern, 
will soon take up many times its own volume of air, as 
will appear by the rise of the mercury in the air-jar. In 
this case it absorbs more oxygen than nitrogen, the residual 
air having only eight per cent, of oxygen in it. On heating, 
it again parts with the gas it has absorbed. The power of 
absorption seems to depend entirely on the natural elasticity 
of the gas, and not at all on its affinity for carbon. Those 

334. What is coal ? How does anthracite differ from bituminous 
coal ? 335. What is charcoal ? How is the best made ? What 
are its powers of conduction ? Is it a changeable substance ? 336. 
What is said of its power of absorbing gases ? What gases are most 
absorbed by it ? 



CARBON. 217 

gases that are most easily reduced to a fluid condition by cold 
and pressure, are most abunaantly absorbed by charcoal. 
Charcoal from hard wood with fine pores has this property in 
the highest degree. TLi js charcoal from box-wood freshly 
prepared, will absorb of ammoniacal gas 90 times its own 
volume ; of muriatic aeid gas 85 times ; of sulphureted hy- 
drogen 81 times ; of nitre us oxyd 40 times ; of carbonic acid 
32 times ; of oxygen 9-25 times ; of nitrogen 1*5 times ; and 
of hydrogen 1*75 times its own volume. 

337. Charcoal also has the power of absorbing the bad 
odors and coloring principles of most animal and vegetable 
substances. Tainted meat is made sweet by burying it in 
powdered charcoal, and foul water is purified by being strain- 
ed through it. The highly coiored sugar syrups are com- 
pletely decolorized by being passed through sacks of animal 
charcoal, (bone black,) prepared by igniting bones. It also 
precipitates bitter principles, resins, and astringent substances 
from . solution. Common ale <~r porter becomes not only 
colorless, but also in a ^ood degree deprived of its bitter 
principles, by being healed with and filtered through animal 
charcoal. This propert) is lost by use, and regained by 
heating it afresh. Its power of absorption seems similar 
to that possessed by spongy pla f, 'num, (212.) Hydrogen, in 
small quantity, is very obstinately retained in the pores of 
charcoal, and water is consequently always produced from 
the combustion of carbon in pure oxygen gas. Carbon has 
a greater affinity for oxygen at high temperatures than any 
other known substance, and for this reason it is useful in 
reducing oxyds of iron and other oxyds to the metallic state. 

1. Compounds of Carbon with Oxygen. 

338. Carbon unites with oxygen in two proportions, to 
form carbonic oxyd and cirbonic acid, whose composition is 
thus expressed : 

Composition by weight. 



Symbol. Carbon. Oxygen. 

Carbonic oxyd, CO 6 8 

Carbonic acid, C0 2 6 16 



"What rule regulates this ? Mention somp instances of the amount 
of absorption. 337. How does it affect bad odors and vegetable 
colors ? What else does it also remove ? To what is this analogous ? 
What is said of its affinity fo oxygen ? 338. Name the compounds 
of carbon with oxygen and their composition. 
19 



218 



NON-METALLIC ELEMENTS. 



339. Carbonic Acid. (C0 2 .) — History. — This is the sole 
product of the combustion of the diamond or any pure car- 
bon in the air, or oxygen gas. It was first recognised and 
described by Dr. Black, in 1757, under the name of fixed 
air. This philosopher proved that limestone and magne- 
sian rocks contained a large quantity of this gas in a state of 
solid combination with the earths, and also that it was freely 
given out in the processes of fermentation, respiration, and 
combustion. 

340. Preparation. — Carbonic acid is easily procured by 
treating any carbonate with a dilute acid. Carbonate of 
lime, in the form of marble powder, is usually employed for 
this purpose ; it is put with a little water into a wide-mouth- 
ed bottle, (&,) (like that used in 308 ;) sulphuric or hydro- 
chloric acid is turn- 
ed in at the tube 
funnel, when the gas 
is set free with effer- 
vescence, and es- 
capes through the 
bent tube. If it is 
wished to have the 
gas dry, it is passed 
over dry chlorid of 
calcium in the hori- 

£*"*"^ J zontal tube t, which 
completely removes 
every trace of moisture from it. Its weight enables us to 
collect it in dry bottles (a) by displacement of air, as in the 
case of chlorine, (260.) No heat is required, and the acid is 
added in small successive portions, the gas being freely evol- 
ved at each addition. If the gas is not required dry, the long 
chlorid of calcium tube may be dispensed with. When ob- 
tained by the action of monohydrated nitric acid on carbonate 
of ammonia, the carbonic acid evolved retains a white cloudy 
appearance, even after passing through water, which renders 
it visible, a point of some importance in experiments with 
this gas. 

This gas can also be collected over the pneumatic trough, 
not being absorbed by water so rapidly but that it may be 
thus managed well enough for experimental purposes. 




339. Give the history of carbonic acid. 340. How is it prepared ? 
How is it dried ? How may it be collected ? 



CARBON. 219 

341. Properties. — At the common temperature and 
pressure, carbonic acid is a colorless, transparent gas, with 
a pungent and rather pleasant taste and odor. At a tempe- 
rature of 32°, and a pressure of 30 to 36 atmospheres, it is 
condensed into a clear limpid liquid, not as heavy as water, 
which freezes by its own evaporation into a white, snow-like 
substance. We have already described (137) the apparatus 
and process by which this interesting experiment is performed. 
Carbonic acid is about once and a half as heavy as common 
air, having a specific gravity of 1*524 ; and 100 cubic inches, 
therefore, weigh 47*26 grains. 

342. Cold water recently boiled absorbs about its own 
volume of carbonic acid gas, but with pressure much more 
will be taken up, in quantity exactly proportioned to the 
pressure exerted. The solution has a pleasant acid taste, and 
temporarily reddens blue litmus paper. The « soda water,' 
so much used as a beverage, is usually only water strongly 
impregnated with carbonic acid, the soda being generally 
omitted in its preparation. The effervescence of this, as well 
as of small beer and sparkling wines, is due to the escape of 
this gas. Natural waters have usually more or less of this 
gas dissolved in them ; and some mineral springs, like the 
Saratoga and Ballston springs, and the Seltzer water, are 
highly charged with carbonic acid. 

343. Carbonic acid instantly extinguishes a burning 
taper lowered into it, even when mingled with twice or 
three times its bulk of air. Fresh lime-water agitated with 
this gas, rapidly absorbs it, becoming at the same time 
milky, from the production of the insoluble carbonate of 
lime. In this way the presence of carbonic acid is easily 
detected, and this gas distinguished from nitrogen. 

344. Death follows the inspiration of carbonic acid, 
even when largely diluted with air. It kills by a specific 
poisonous influence on the system resembling some narcotics, 
and is unlike nitrogen (291) in this particular, which kills 
only by exclusion of air, as water drowns. Instances of 
death from sleeping in a close room where a charcoal fire is 

341. What are the properties of carbonic acid? At what tempe- 
rature and pressure does it solidify ? What is its gravity ? 342. 
How much of it does water absorb ? What is said of the solution ? 
Is it found in natural waters ? 343. How does it affect combustion ? 
What test is there for it ? 344. How does it affect life when 
breathed ? Is it poisonous ? 



220 NON-METALLJ-C ELEMENTS. 

burning, and from descending into wells which contain car- 
bonic acid, are lamentably frequent. The latter accident 
may always be avoided by taking the obvious precaution to 
lower a burning candle into the well before going into it, 
when if the candle burns, all may be considered safe, but its 
being extinguished is certain evidence that the well is unsafe. 
Wells containing carbonic acid may often be freed from it 
by lowering a pan of recently heated charcoal into the well, 
which will soon absorb thirty-five times its bulk of this gas, 
(336,) thus removing the evil. 

345. Numerous natural sources evolve large quantities of 
carbonic acid, particularly in volcanic districts. It abounds 
also, in common with gases to be mentioned hereafter, in 
coal mines ; it is produced abundantly by those explosions, 
which are so often fatal in the mires, and kills by its poi- 
sonous influences those who may escape the explosion. The 
Grotto del Cane, in Italy, (dog's grotto,) is a noted instance 
of the natural occurrence of this gas. 

It is always present in the air, (302,) being given off by 
the respiration of all animals, and besides the other sources 
already named, is an invariable product of all common cases 
of combustion. 

All the carbon which plant3 secrete in the process of their 
developement, is derived either from the carbonic acid of the 
atmosphere, which they decompose by the aid of sun-light 
by their green leaves, retaining the carbon and returning the 
pure oxygen to the air; or it is absorbed by their rootlets and 
then decomposed by the sun's light at the surface of the leaf. 

346. Carbonic acid is formed if equal volumes of its 
two constituent gases condensed into one. For this reason 
the air suffers no change of bulk from the enormous quan- 
tities of this gas which are hourly formed and decomposed 
on the earth. This acid unites with alkaline bases, forming 
an important class of salts, (the carbonates,) which are all 
decomposed by any stronger acid, with the escape of car- 
bonic acid. 

347. Carbonic Oxyd, (CO.) — Preparation. — This gas is 
produced in several ways. (1.) By passing carbonic acid 



How may these accidents be avoided ? 345. What natural sources 
of it are named ? Is it in the air ? Whence do plants get their 
carbon? 346. Give its composition by volume. What class of 
salts does it form ? 347. How is carbonic oxyd prepared ? First ? 



CARBON. 221 

over fragments of coal heated to redness in an iron tube, 
the oxygen gains another equivalent of carbon, and carbonic 
oxyd results. (2.) Oxalic acid, (C 2 3 ,HO-f 2HO,) when 
treated with five or six times its weight of strong sulphuric 
acid, is decomposed, the acid takes the water of the oxalic 
acid, and a gas escapes, which is formed of equal measures 
of carbonic acid and carbonic oxyd. C 2 3 yield CO and 
C0 2 . Carbonic acid is absorbed by standing over water, or 
by agitation of the gas with an alkali, and the carbonic oxyd 
is left pure. (3.) The best method is that recommended by 
Dr. Fownes, which is to mingle in a capacious retort eight 
or ten parts of sulphuric acid with one part of dry finely 
powdered yellow prussiate of potash. The salt is entirely 
decomposed by a gentle heat, yielding an abundant volume 
of pure carbonic oxyd. 

348. Properties. — This is a colorless, almost inodorous 
gas, burning with a beautiful pale blue flame, such as is often 
seen on a freshly fed coal fire. Its specific gravity is a little 
less than that of air, or '973 ; and 100 cubic inches of it weigh 
30*20 grains. It is not absorbed by water, does not render 
lime-water milky, and explodes feebly with oxygen. It is not 
irrespirable, but is even more poisonous than carbonic acid, 
producing a state of the system resembling profound apo- 
plexy. This gas is very largely produced in the process of 
reducing iron from its ore in the high furnace. 

Carbonic oxyd is formed of half a volume of oxygen and 
one volume of carbon, or two volumes of carbon and one of 
oxygen condensed into two volumes. 

349. Carbonic oxyd combines with chlorine and some other 
elementary bodies, forming compounds in which it appears to 
act the part of an element. Its union with chlorine is pro- 
duced by the influence of light, and the product is called phos- 
gene gas. This is a pungent, highly odorous, suffocating 
body, possessing acid properties, and decomposed by water. 

2. Compounds of Carbon with the Chlorine Group. 

350. The compounds of oxygen and carbon already 
mentioned are the most important which carbon forms with 



Second ? third ? Which mode is preferred ? 348. What are its 
properties ? What is its density ? How does it affect life ? In 
what art is it largely produced ? 349. What compound does it 
form with chlorine ? What is its name ? 
19* 



222 NON-METALLIC ELEMENTS. 

the first class of the non- metallic elements. But there are 
certain others which we will briefly mention. They are — 

Composition by weight. 



Chlorid of carbon, 
Perchlorid of carbon, 
Dichlorid of carbon, 

Bisulphuret of carbon, 


Symbol. 

CCl 

C2C13 

C 2 C1 

CSa 


Chlorine. 

35-41 

106-23 

35-41 

Sulphur. 

32-18 


Carbon. 

6 

12 

12 

6 



351. The chlorids of carbon are obtained from the action 
of chlorine on a peculiar body formerly called Dutch liquid,* 
produced from the union of chlorine, hydrogen, and carbon. 
We shall refer any further mention of these compounds to 
the organic chemistry. 

352. Bisulphuret of carbon is produced by passing the 
vapor of sulphur over fragments of recently prepared char- 
coal, heated to redness in a porcelain tube, which is so 
inclined that the heavy volatile fluid may run down in vapor 
and be condensed in an ice-cold vessel filled with water. 
This product is redistilled, to purify it. 

353. Properties. — Bisulphuret of carbon, when pure, is a 
colorless liquid, but has usually a yellowish tint ; its power 
of refracting light is very remarkable. It has a most dis- 
gusting odor, and boils at 110°. lis density is 1-27, and in 
vapor 2-68. It dissolves sulphur, phosphorus, and iodine, 
these bodies being deposited again in beautiful crystals by 
the evaporation of the sulphuret of carbon. It burns in the 
air at about 600°, with a pale blue ilame. It forms an ex- 
plosive mixture with oxygen, and a combustible one with 
binoxyd of nitrogen. It dissolves easily in alcohol and ether, 
and is precipitated again by water. 

3. Compounds of Carbon with Nitrogen. 

354. Carbon forms an unimportant compound with phos- 
phorus, but with nitrogen it unites to form one of the most 
remarkable compound bodies known to chemists. This is 



350. What other compounds are named of carbon with oxygen ? 
351. What are the chlorids of carbon ? 352. How is the bisulphuret 
of carbon prepared ? 353. What are its properties ? What does it 
dissolve ? In what is it soluble ? 354. What is cyanogen ? 

* From its being discovered at Harlem, in Holland, by an asso- 
ciation of Dutch chemists. 



silicon. 223 

called cynanogen, and is composed of one equivalent of nitro- 
gen and two of carbon, or NC 2 . Although a compound, it 
acts in all respects like an element, entering into combina- 
tion with the same energy with which elements unite. Its 
production and properties are referred to the organic chem- 
istry, where it can be better understood. 

Equivalent, 22-18. Symbol, Si. Density in vapor, (hypo- 
thetical,) 15-29. 

355. Common quartz, or rock crystal and gun-fint, are 
very familiar substances ; these are the compound of sili- 
con and oxygen, known as silica, or silicic acid. Silicon 
is, however, a substance very rarely seen, even by chemists, 
because it never occurs in nature, and is very difficult to 
prepare. Silica, its compound with oxygen, is, next to 
oxygen, the most abundant, and one of the most important 
substances known. It is calculated that it forms one-sixth 
part of the crust of the globe. 

356. Preparation of Silicon. — Silica retains its oxygen 
so powerfully that it is very difficult to separate it and 
leave the pure silicon. Silicon may be procured, however, 
by an indirect process, which is to decompose the double 
fluorid of silicon and potassium, (2SiF 3 -f 3KF.) This is 
a white powder, like starch, and very sparingly soluble in 
water. To decompose this, it is mixed with about its own 
weight of the metal potassium cut in 
small pieces, and put in a test tube of 
hard glass, which is then heated over a 
lamp. As soon as the tube is heated 
on the bottom to redness, a vivid ignition 
is seen to take place, and to spread 
through the whole mass. The residue 
after this ignition, when cool, is treated 
with water, which dissolves all the fluo- 
rid of potassium that has been formed in the process, leaving 
behind the silicon. Thus the (2SiF 3 + 3KF) acted on by 
6K give 9KF and 2Si. 

How does it act ? Where do we consider it ? 355. Of what is 
silicon the basis? Is it a natural substance? How abundant is 
silica ? 356. How is silicon prepared ? Give the reaction. 




224 



NON-METALLIC ELEMENTS. 



357. Properties. — Silicon is a dark nut-brown powder, 
without metallic lustre, and a non-conductor of electricity. 
Heated in air or oxygen it burns, forming silica. If heated 
in a close vessel, it shrinks and becomes more dense. Be- 
fore ignition it is soluble in hydrofluoric acid, but after this 
it is insoluble, and is incombustible in the air or oxygen gas. 
It seems then to resemble the graphite variety of carbon. 
These two diverse conditions of silicon are probably con- 
nected with the two states in which silica occurs. This 
element has been often called a metal, and named accordingly 
silicium ; but if power to conduct electricity, and the posses- 
sion of a metallic lustre, are attributes of a metal-, silicon has 
no claim to be so classed. Its real affinities are more with 
carbon. 

Compounds of Silicon. 

358. The known compounds of silicon are not numerous; 
those mentioned in this section are — 

Composition. 



Symbol. 


Silicon. 


Oxygen. 


Si0 3 


22-18 


24 

Chlorine. 


SiCl 3 


22-18 


106-23 
Bromine. 


SiBr 3 


22-18 


234-78 

Fluorine. 


SiF 3 


22-18 


56-10 
Sulphur. 


SiSa (probably) 


22-18 


66-27 



Silicic acid, (silica,) 
Chlorid of silicon, 
Bromid of silicon, 
Fluorid of silicon, 
Sulphuret of silicon, 

The similarity of composition in these bodies is a remark- 
able circumstance, as will be seen at a glance by inspecting 
their formulas. 

359. Silicic acid or Silica, (Si0 3 .) — This oxyd of sili- 
con exists abundantly in nature in the form of rock crystal, 
agate, common uncrystallized quartz, silicious sand, &c. ; it 
also enters largely into combination with other substances to 
form the rock masses of the globe. It is a very hard sub- 
stance, easily scratching glass, and is difficult to reduce to a 
powder; its specific gravity is 2*66. It is infusible alone, 



357. What are its properties ? How does heat affect it ? What 
two states of it are noticed ? To what are these analogous ? Why 
not consider it a metal ? 358. What compounds of silicon are 
named ? 359. What is silicic acid ? Give its properties. 



SILICON. 



225 



except by the power of the compound blowpipe. It dissolves 
with effervescence in fused carbonate of soda or potash ', the 
effervescence being due to the escape of carbonic acid from 
the alkali, which is replaced by the silicic acid. No acid 
(except the hydrofluoric) has any effect on silica. When in 
its finest state of division it is still harsh and gritty to the 
touch or between the teeth. 

360. Silica is known in two very unlike conditions — its 
insoluble or common condition, and its soluble or hydrous 
state. When silica is dissolved in a fused alkali, ancf then 
again this silicated alkali in a strong acid, as the hydrochloric, 
we obtain on evaporating the solution to a small bulk, a trem- 
ulous gelatinous mass, which is soluble silica. If an excess 
of alkali is used, the silicate formed is soluble in water, and is 
sometimes called the liquor of flints. If this soluble silica is 
dried, it is again reduced to its insoluble condition. Most 
natural waters contain some small portion of soluble silica ; 
it has been often seen in this state in mines ; and on breaking 
open silicious pebbles, the central parts are sometimes semi- 
fluid and gelatinous. The hot waters of the great geysers in 
Iceland, and of other hot springs, also dissolve large quanti- 
ties of silica, probably aided by alkaline matter. Agates, 
chalcedony, cornelian, &c. have been deposited from the sol- 
uble state. It is in this condition, no doubt, that silica enters 
the substance of many vegetables, as, for instance, the reeds 
and grasses, which have often a thick crust of silica on their 
bark. It also produces most beautiful petrifactions of natu- 
ral objects, as corals, shells, and many vegetables, completely 
replacing the organic matters, and turning them into solid 
quartz or elegant chalcedonies and agates. 

361. The uses of silica in the arts are very important. 
It is the basis of all glass, being fused with alkalies to form 
this useful and beautiful substance, (see glass and pottery,) 
and also of porcelain and all kinds of potters' ware. In 
chemistry its uses are chiefly confined to certain analytical 
operations of no importance to our present object. 

362. It is called an acid, from the power it has of acting 
the part of a powerful acid at high temperatures. At ordi- 



What dissolves it ? 360. What two unlike conditions of silica are 
named ? How is the soluble condition produced ? How do we find 
it in nature ? What function does it discharge ? 361. What are the 
uses of silica ? 362. Why is it called an acid ? 



226 NON-METALLIC ELEMENTS. 

nary temperatures its insolubility renders its acid properties 
insensible to all our usual tests for acids. When by a suffi- 
cient temperature it is rendered soluble, we see its acid char- 
acter very distinctly in the ease with which it completely 
saturates the most powerful alkalies. 

363. Chlorid of silicon is formed by passing a current of 
dry chlorine gas over silicon heated. to redness in a tube of 
porcelain or glass ; or, more simply, by employing, in place of 
silicon, the finely powdered silica, mixed with powdered 
charcoal in the same tube, and treated in the same manner. 
The carbon takes the oxygen of the silica at the high temper- 
ature, and the chlorine unites with the silicon to form a very 
volatile chlorid of silicon, which is condensed in a cold 
receiver, while the excess of chlorine, and the carbonic oxyd 
formed in the process, escape as gases. The chlorid of sili- 
con is a colorless liquid, denser than water, and boils at 124°. 
Water decomposes it, forming hydrochloric acid and silica. 

There is a bromid of silicon possessing the same properties 
and formed in an exactly similar manner. 

364. Fluorid of silicon, (fluosilicic acid.) — The affinity 
existing between fluorine and silicon is one of the strongest 
known to chemists. .We have already mentioned this while 
speaking (230) of fluorine. Fluorid of silicon may be pro- 
cured by heating a mixture of powdered fluor-spar and 
quartz with strong oil of vitriol : 

Fluor-spar. Silica. Sul. acid. Sul. lime. Water. Fluorid silicon. 
3CaF + Si03 -f. 3(S03,HO) = 3(CaO, S0 3 ) -f 3HO + SiF 3 . 

Being rapidly absorbed by water, it must be collected over 
mercury. It forms dense white vapors with the moisture of 
the air, as soon as it comes in contact with it. 

365. Properties. — This is a dense, colorless gas, having 
a specific gravity of about 3*60, air being 1 : it has lately 
been rendered fluid by Dr. Faraday, with a cold of 160° be- 
low zero, and a pressure of about nine atmospheres. When 
this gas is passed into a vessel of water, it is decomposed, 
each bubble becomes incrusted in a shell or sack of pure 
silica, and retains its form more or less as it rises through 



Why are its acid properties concealed? 363. How is chlorid of 
silicon formed? What are its properties ? 364. How is fluorid of 
silicon formed ? Give the reaction on the black-board. Is it ab- 
sorbed ? 365. Give its properties. How does it behave in contact 
with water ? 



BORON. 227 

the water, which soon becomes milky, from the quantity of 
finely divided silica suspended in it. Meanwhile the water 
becomes a solution of hydrofluosilicic acid, 2(SiF 3 ) + 3HF, 
which is formed from the decomposition of one-third of the 
fluorid of silicon, giving silica and hydrofluoric acid, which 
last unites with the remaining fluorid of silicon, and dissolves 
in water. The fluosilicic acid gas should not be passed 
directly into water, but the tube should dip under the surface 
of a portion of mercury in the bottom of the bottle holding 
the water ; if this precaution is neglected, the open end of 
the tube soon becomes plugged up with silica, and the gas 
bottle may burst. This acid solution is decomposed by heat. 
It forms almost insoluble salts (double fluorids) with the 
metals potassium and sodium, and hence is of value in 
separating these substances from their solutions. 

366. Silicon, when heated with sulphur, unites with it, 
forming a sulphuret, which is a white earthy compound, 
(SiS 3 .) It is decomposed by water into silica and sulphureted 
hydrogen. 

13. BORON. 

Equivalent, 10 # 90. Symbol, B. Density in vapor, (hypo- 
thetical,) *751. 

367. The only compound of boron commonly known is 
borax, a salt much used in the arts. Boracic acid (its 
compound with oxygen) is found in the waters of certain 
lagoons or lakes in Tuscany, from which large quantities of 
it are introduced to commerce. This acid, accompanied by 
sulphur and selenium, is also sublimed among the volcanic 
products of the volcanoes at the Lipari islands, and in other 
similar places. 

368. Boron is prepared by a process very similar to that 
which produces silicon. The double fluorid of boron and 
potassium being treated with potassium in an iron vessel 
heated to redness, gives us KF, BF 3 +3K=4KF + B. The 
boron remains as a dark olive-green powder, after the 
soluble fluorid has been dissolved out by water. Heated in 



What reaction takes place ? What caution is required ? 366. 
What is the sulphuret of silicon ? 367. Give the equivalent and 
symbol for boron. How is it found associated in nature ? 368. How 
is boron prepared ? 



228 



NON-METALLIC ELEMENTS. 



air to about 600°, it burns brilliantly, producing boracic acid. 
It does not conduct electricity, is insoluble in water and all 
other neutral fluids. Heated out of contact with air, it suf- 
fers no change. It is easy to see how similar these charac- 
ters are to those possessed by carbon and silicon. 

Compounds of Boron. 
369. The compounds of boron mentioned under this head 



are 



Composition by weight. 



Boracic acid, 


Symbol. 
B0 3 


Chlorid of boron, 


BC1 3 


Fluorid of boron, 


BFI3 


Sulphur et of boron, 


BS 3 



Boron. 


Oxygen. 


10-90 


24 




Chlorine. 


10-90 


106-23 




Fluorine. 


10-90 


56-10 




Sulphur. 


10-90 


48-27 



370. Boracic acid, as just mentioned, is found native, and 
is also produced, when boron is burnt in oxygen or common 
air. It is easily prepared by decomposing common borax 
(borate of soda) dissolved in about 4 parts of hot water, with 
one-third its weight of sulphuric acid. Sulphate of soda is 
formed and boracic acid set free, which, being nearly insolu- 
ble in cold water, is deposited in pearly scales as the solution 
cools. When quite cold, the supernatant fluid is poured off, 
and the white scales washed with cold water. This is a 
hydrate of boracic acid, B0 3 + 3HO. Half this water of 
crystallization is expelled at 212° ; when it melts into a 
fusible glass, which is brittle and clear when cold. Boracic 
acid is little soluble in cold, but readily in hot water ; and its 
watery solution cannot be evaporated without the steam 
carrying away a large portion of the acid. The glassy acid 
is, however, quite fixed, even at a red heat. Alcohol dis- 
solves boracic acid, and the solution burns with a peculiar 
and quite characteristic green color. Its acid powers are 
feeble ; its salts (borates) being all decomposed even by 
weak acids. It turns blue litmus to a port-wine color, but 



What are its properties ? To what is it likened? 369. Name the 
compounds of boron in this section. 370. How is boracic acid 
formed ? What are its properties ? What is the glacial acid ? Can 
the watery solution be evaporated ? What is its proper solvent ? What 
characteristic property has it ? What of its acid characters ? 



HYDROGEN. 229 

lloes not redden it, and affects yellow turmeric paper like an 
alkali, turning it brown. 

371. It is used in the arts to promote the fusion of other 
bodies, which it does in a remarkable degree, by the fusi- 
bility of all its salts. It is also much used as a flux in blow- 
pipe operations and in the laboratory. 

372. Chlorid of boron is formed in the same manner as 
the chlorid of silicon, boracic acid being used in place of 
silica. It is a dense, colorless, transparent gas at ordinary 
temperatures, having a specific gravity of 4*09 ; and by cold 
and pressure it may be reduced to a fluid. It has a pungent, 
acid smell, and forms thick vapors in the air. It is absorbed 
by water, and is collected over mercury. 

373. Fluorid of boron. — The same process by which 
fluorid of silicon is prepared yields fluorid of boron, by sub- 
stituting boracic for silicic acid. The gas is similar, and 
has a density of 2*362, and an avidity for water which 
causes it to form dense fumes in the air. It is decomposed 
by water, hydrofluoboric acid being formed, which is per- 
fectly analogous to hydrofluosilicic acid. 

374. The sulphur et of boron is a white powder formed 
from the combustion of boron in the vapor of sulphur, and is 
quite similar to the sulphuret of silicon. It is decomposed 
by water, boracic acid and sulphureted hydrogen being 
formed. 

CLASS VI. 

HYDROGEN. 

Equivalent, 1. Symbol, H. Density, 0-069. 

375. History. — Hydrogen was first described as a dis- 
tinct gas by the English chemist Cavendish, in 1766, and 
was called by him inflammable air. It had previously 
been confounded with other combustible gases, several of 
which had been long known. Hydrogen exists abundantly 
in nature as a constituent of water, whence its name, (193.) 
It is also a constituent of nearly all animal and vegetable 

371. Of what use is boracic acid ? 372. What is said of the 
chlorid of boron ? 373. What of the fluorid ? To what are it and the 
chlorid similar ? 374. What of the sulphuret of boron ? 375. Give 
the equivalent, symbol, and density of hydrogen. When and by 
whom was hydrogen discovered ? In what manner does it exist ii 
■ature ! 
20 



230 



NON-METALLIC ELEMENTS. 



substances, in which it exists in such proportions to oxygen 
as to form water during the combustion of these bodies. 

376. Preparation. — This gas is best prepared for use 
by the action of dilute sulphuric acid on zinc or iron. 
Zinc is usually .preferred as yielding a purer gas. The acid 
is diluted with four or five times -its bulk of water, and the 




operation may be conducted in a glass retort, or more 
conveniently in the small way by using a gas bottle (a) con- 
taining the zinc in small fragments, to which the dilute acid 
is turned through the tube funnel, (b.) The shorter tube 
(f) with a flexible joint conveys the gas to the air- jar, (e,) 
standing in the cistern, (g.) No heat is required in this 
operation. An ounce of zinc yields 615 cubic inches of 
hydrogen gas. When it is required in large quantity, a 
leaden pot or stone jar, properly fitted, and holding a gallon 
or more, is used to contain the requisite charge of materials, 
and the gas is stored for use in a gas-holder such as has 
already been described and figured, ( 258. ) Zinc is 
readily granulated, by being turned when melted, into cold 
water. 

377. Properties. — Hydrogen when pure is a clear color- 
less gas, which no amount of cold and pressure yet obtained, 
has reduced to a liquid form. It refracts light very power- 
fully, and has the highest capacity for heat of any known 
gas. It is inodorous and tasteless, and may be breathed 
without inconvenience when mingled with a large quantity of 
common air. It cannot, however, support respiration alone, 
and an animal plunged in it soon dies of suffocation. Water 



376. How is it prepared ? Describe the process. 377. Give the 
properties of hydrogen mentioned in this section. Is it poisonous ? 



HYDROGEN. 231 

absorbs only about one and a half per cent, of its bulk of 
pure hydrogen gas. The voice of a person who has breathed 
it acquires for a time a peculiar shrill squeak. 

378. Hydrogen is the lightest of all known forms of mat- 
ter, being sixteen times lighter than oxygen, and fourteen 
times and a half as light as common air. 100 cubic inches 
of it weigh only 2*14 grains. Soap-bubbles blown with it 
from a bladder rise rapidly in the air ; and it is usually em- 
ployed to fill balloons, being the lightest gas which can be pro- 
duced, and the cheapest, if we except common coal gas. A 
turkey's crop, well cleansed, makes a good balloon on a small 
scale, for the class-room, and very beautiful small balloons 
(from 1^ to 5 feet diameter) are prepared in Paris of gold- 
beaters' skin. Hydrogen is so named from the fact that it 
forms water by its union with oxygen. [Hvdor, water, and 
gennao, to form.) 

379. Hydrogen is the most attenuated form of matter 
with which we are acquainted. We have reason to suppose 
the molecules of this body to be smaller than those of any 
other now known to us. Dr. Faraday, in his attempts to 
liquefy this gas, found that it would leak and escape through 
an apparatus which was quite tight to other gases. Thus 
hydrogen leaked freely with a pressure of 27 or 
28 atmospheres, through stop-cocks that were 
perfectly tight with nitrogen at 50 or 60 atmos- 
pheres. This extreme tenuity, together with the 
remarkable law of diffusion of gases already 
explained, (132,) renders it unsafe to keep this 
gas in any but perfectly tight vessels. A small 
crack in a bell jar, quite too narrow to leak with 
water, will soon render the hydrogen with which 
it may be filled explosive. The superiority in 
diffusive power which hydrogen has over com- 
mon air, is well seen in what is called Mr. Gra- 
ham's diffusion tube, of which a figure is annexed. 
A glass tube 11 or 12 inches long and of convenient size, 
has a tight plug of dry plaster of Paris at the upper end, and 

How does it affect the voice ? 378. "What is said of its density ? 
What do 100 cubic inches weigh ? For what purpose is it used ? 
Give the meaning of the word hydrogen. 379. What is said of the 
molecules of hydrogen ? What was the result of Dr. Faraday's 
experiments on it ? How is its tenuity evident from the law of 
diffusion ? Explain the diffusion tube. 




232 NON-METALLIC ELEMENTS. 

being filled with dry. hydrogen by displacement of air, and its 
lower end put into a glass of water, the hydrogen escapes so 
rapidly through the plaster plug, that the water is seen to rise 
in the tube, so as in a few moments to replace nearly all the 
hydrogen, and the remaining portion of gas is found to be 
explosive. Hydrogen also enters into combination in a smaller 
proportionate weight than any known body, (188,) and con- 
sequently has been chosen as the unit of the scale of equiva- 
lents. Sounds are propagated in hydrogen with but little 
more power than in a vacuum. 

380. Hydrogen is a most eminently combustible gas, 
taking fire from a lighted taper, which is instantly extin- 
guished by being plunged into the gas. It burns with a 
very faint light and a bluish white flame. Its extreme levity 
requires this experiment to be performed in an inverted ves- 
sel like the annexed figure. A dry bottle with its mouth 

downward is well suited to collect this gas by dis- 
placement of air, as the heavier gases are collected 
(260) by the reverse position. When lighted, the 
gas burns quietly at the mouth of the bottle ; and 
the extinguished taper may be relighted by the 
flame at the mouth. If the bottle is suddenly re- 
versed after the gas has burned awhile, the remain- 
ing gas being mixed with common air, will burn 
explosively with a single flash. Three of the most 
remarkable properties of hydrogen are thus shown 
by one experiment, viz : its extreme levity, its 
combustibility, and its explosive union with oxygen. 
If this gas is incautiously mingled with common 
air, or much more with pure oxygen, a severe explosion 
results when the mixture is fired. The eyes or limbs of inex- 
perienced operators have thus too often paid the forfeit by the 
explosion of gas vessels. Particular caution is required not 
to collect any gas from the vessel in which it is generated 
until all the common air is expelled, as well from the genera- 
tor, as from the receiving-vessel or gas-holder. 

381. Pure hydrogen is not yielded by the methods before 



Why was hydrogen chosen as the unit of the scale of equivalents ? 
How are sounds propagated by it? 380. What of the combustibility 
of hydrogen ? How does it burn ? What three remarkable proper 
ties of hydrogen may be shown in one experiment, and how ? What 
caution is given about collecting gases ? 381. Why is hydrogen not 
pure when obtained by the mode described ? 




HYDROGEN. 



233 




described. The gas, 
when obtained from iron, 
has always a peculiar 
and offensive odor, due 
in a measure to the pre- 
sence of a volatile oil, 
formed by the gas with 
the carbon always found 
in iron. That yielded 
by the use of zinc is also 
somewhat impure, both 

having a portion of the metals dissolved in the gas, which 
tinge the flame. Traces of sulphureted hydrogen and car- 
bonic acid are ak/) usually found in hydrogen, being formed 
from the impurities in the metals by which the gas is evolved. 
Some of these impurities, and particularly the vapor of the 
acid, which is carried over mechanically, are removed by 
passing the gas through a second bottle containing an alkaline 
solution, in water or alcohol. It. is generally advisable to 
pass gases through a portion of water or some other fluid 
which will remove from them their impurities. 

382. Water is the sole product of the combustion of 
hydrogen in common air, or in oxygen gas. 
The combustion of a jet of hydrogen, and 
the production of water from this combus- 
tion, and certain musical tones, are all neatly 
shown by an arrangement like the annexed 
figure. The gas is generated in the bottle a, 
and a perforated cork at the mouth has a 
small glass tube, from the narrow end of 
which the stream of hydrogen is lighted. 
An open glass tube (6) held over this flame, 
is at once bedewed by the water produced in 
the combustion, and a musical tone is gene- 
rally given out, by the interruption which 
the flame suffers from the rapid current of 
air, ascending through the tube, which causes it to 
flicker, and being momentarily extinguished, there occur 
a series of little explosions. The pitch of the note pro- 




With what is it contaminated ? How may it be purified ? 382. 
What is the product when hydrogen is burnt in air or oxygen ? De- 
scribe the philosopher's lamp and the musical tones with hydrogen. 
20* 



# 



234« NON-METALLIC ELEMENTS. 

duced depends on the length and size of the glass tube, 
and the size of the jet of hydrogen, which should be small. 
If the jet is fitted to the gas-holder, we can modulate the tone 
by turning the key of the stop-cock regulating the supply of 
gas. The little gas bottle (a) with a small jet is often called 
" the philosopher's lamp." 

1. Nature of Hydrogen. 

383. The real nature of Hydrogen was for a long time 
not well understood. It was associated with oxygen and 
chlorine, because it was supposed to bear the same relations 
to hydrochloric acid that oxygen bears to sulphuric and 
chloric acids. Dr. Kane insisted on the highly electro-posi- 
tive nature of hydrogen ; and, to prove to the satisfaction of 
chemists that this gaseous body was in reality more nearly 
allied to iron, zinc, copper, and manganese, than to any other 
class of bodies, he showed that the compounds of hydro- 
gen with oxygen, chlorine, iodine, sulphur, &c, were almost 
universally electro-positive in combination, and possessed 
basic characters, derived from the pre-eminent electro-positive 
energies of hydrogen itself. It is now the belief of nearly 
all philosophical chemists, that hydrogen is most closely 
allied to the metals, particularly to zinc and copper; that the 
chlorids, iodids and fluorids of hydrogen, although they pos- 
sess the characters which we assign to acids, resemble in 
many respects the chlorids, iodids, &c, of the same metals; 
that in fact hydrogen is a metal, exceedingly volatile, proba- 
bly standing in that respect in the same relation to mercury 
that mercury does to platinum, but still possessed of all truly 
chemical peculiarities of the metallic state, and no moro 
deprived of the common-place qualities of lustre, hardness, or 
brilliancy, than is the mercurial atmosphere which fills the 
apparently empty space in the barometer tube.* The vapor 
of mercury, and of other volatile metals, is like hydrogen a 
non-conductor of heat and electricity ; but we cannot on this 
account deny their metallic character. We must not forget 
that hydrogen may yet, by sufficient cold and pressure, be 



383. What is said of the nature of hydrogen? To what is it 
compared ? What is the present opinion of chemists about hydrogen ? 
What analogous cases have we in the volatile metals ? 

* Dr. Kane's Elements, page 409, English edition. 



HYDROGEN. 235 

made solid or fluid, when doubtless we shall see its resem- 
blance in physical, as well as we now do in chemical charac- 
ters, to the metals. The propriety of giving hydrogen the 
place in our classification which it occupies, will now be 
more apparent to those who have usually seen it placed next 
to oxygen. 

2. Compounds of Hydrogen with Oxygen. 

384. There are two known compounds of hydrogen with 
oxygen, viz : 

Composition by weight. 

Symbol. Hydrogen. Oxygen. 
Water, (the oxyd of hydrogen,) HO 1 8 

Binoxyd of hydrogen, HO2 1 16 

The first of these is the most remarkable compound known, 
whether we contemplate it in its purely chemical relations, or 
in reference to the wants of man and the present condition 
of the globe. 

385. Water. — The reader has already been made familiar 
with the composition of water, as formed by the union of 
two volumes of hydrogen and one of oxygen. Frequent 
mention has been made of it in the foregoing pages of this 
work, as an illustration of the principles of combination and 
decomposition. We cannot properly understand the produc- 
tion of hydrogen by any process, without studying at the 
same time the constitution of water. In examining the com- 
pounds of hydrogen and oxygen, as in all other chemical in- 
vestigations, we can pursue the subject either analytically or 
synthetically ; that is, we can either form the compounds 
by the direct union of the elements, or we can decompose 
these compounds, and thus gain a knowledge of their consti- 
tution. 

386. The Decomposition of Water. — The simplest case 
of the decomposition of water is that where metallic potas- 
sium is employed, which is directly oxydized by the water, 
hydrogen being evolved. The reaction is K + HO=KO-f-H, 
which last is given off. 

387. The voltaic decomposition of water has already 
been described, (235,) and we need not repeat it here. It 

384. What are the compounds of hydrogen and oxygen ? Give their 
composition. 385. What is said of the constitution of water ? How 
can we proceed in studying the compounds of hydrogen and oxygen ? 
386. What is the simplest case of the decomposition of water ? 



\ ■ 



236 



NON-METALLIC ELEMENTS. 




is, however, by far the most satisfactory means of decom- 
position which we possess, since both 
elements of the water are evolved in a 
pure form and in exact atomic propor- 
tions. In fact this is a complete ex- 
perimentum crucis, being both analysis 
and synthesis ; for we may so arrange 
the single tube apparatus, that the mix- 
ed gases from the electrolysis of water 
may be fired by the ignition of the wires, 
as soon as a sufficient volume of the 
mixture has been collected. A com- 
plete absorption follows the explosion, 
and the gases again go on collecting. 
The oxygen which is dissolved in water 
from the air, always makes this experi- 
ment, when accurately performed, seem 
to show a very slight excess in the oxygen. 

388. The decomposition of water by heat in the manner 
here figured is one of the best methods of analyzing water, 
both from its satisfactory results, and its cheapness and ease 
of accomplishment. An iron tube, (as a gun-barrel,) or a 

tube of porcelain, c, is laid 
horizontally over a fire, or 
heated in a furnace to full 
redness. The tube con- 
tains clean turnings of 
iron, or better, a bundle 
of clean iron wire of 
known weight. A small 
retort (a) holding a little 
water is boiled by a spirit lamp at the moment when the 
iron is at a full red heat ; the vapor of the water coming into 
contact with the heated iron, is decomposed, the oxygen is 
retained by the iron, forming oxyd of iron, and the hydro- 
gen is given off from the tube,y, which may be made to con- 
duct it, either to the pneumatic trough, or to a gas-holder like 
the one already figured, (258.) For every eight grains of 
weight acquired by the iron, 46 cubic inches of hydrogen, 
weighing one grain, have been evolved. 




387. What is the voltaic mode of decomposition ? 388. Describe the 
method of decomposing water by heat. What is the reaction in this 
case ? How much hydrogen do we get for eight grains of gain in the iron? 



HYDROGEN. 237 

389. The iron in this case is evidently substituted for 
the hydrogen, taking its place with the oxygen to form the 
oxyd of iron, while the hydrogen is set free. The oxyd of 
iron resulting from this action is the same black oxyd which 
the smith strikes off in scales under the hammer, being a 
mixture of protoxyd and peroxyd. This case of affinity is 
an interesting one, because it is seemingly reversed when, 
under the same circumstances, we pass a stream of hydro- 
gen over oxyd of iron, by means of which the iron is 
reduced to the metallic state, and water is produced. It will 
be remembered that we cited this instance, (211,) while 
speaking of the influence of quantity of matter in determin- 
ing the nature of the chemical changes which might take place 
among bodies. 

390. The decomposition of water by zinc or iron in the 
ordinary mode of procuring hydrogen can now be satisfac- 
torily explained. As already stated, dilute sulphuric acid is 
added to fragments of zinc, or to iron filings, and hydrogen 
gas is given off abundantly with effervescence. The action 
continues until either the zinc or acid is all consumed, or 
until there is no longer water enough to dissolve the resulting 
sulphate of zinc. Thus we take 

Zn + S0 3 + HO, and we obtain H + (S0 3 + ZnO.) 

In other words, the zinc has taken the place before occupied 
by hydrogen, while the oxygen of that atom of water has 
united with the zinc, to form oxyd of zinc. * The acid dis- 
solves this oxyd as fast as it is formed, thus making a con- 
stantly renewed surface of clean metal. The water serves 
to dissolve the sulphate of zinc as fast as it is formed. Zinc 



389. What is the action of the iron in this case ? What oxyd is 
formed ? 390. How is the decomposition of water by zinc explained ? 
Give the reaction. How is it in case we employ hydrochloric acid ? 
{Note.) What does the acid do, and what the water ? How do the 
electrical relations affect this change ? 



*We can state this reaction in much more simple terms, by em- 
ploying hydrochloric acid in place of sulphuric acid : we have then 

Hydrochloric acid -f- zinc. Hydrogen + chlorid of zinc. 
HCl-fZn and obtain H + ZnCl. 

In this case there is no oxydation, for the same change is made when 
dry hydrochloric acid is used, and consequently no compound con- 
taining oxygen is present. 



238 NON-METALLIC ELEMENTS 



■i 



and iron decompose water even, without the aid of an acid, 
but only with great slowness, and the action ceases as soon as 
the metal is covered by the coating of the oxyd thus formed, 
which protects it from further corrosion. A dilute acid 
removes this coating of oxyd, and also aids, no doubt, in 
establishing such electrical relations as to make the zinc 
highly electro-positive. That this is the fact, seems quite pro- 
bable, because pure zinc is hardly affected by dilute acids, 
and we have already noticed the effects of amalgamation 
(161, note) in rendering the zinc incapable of decomposing 
water. 

391. It was formerly said that the presence of an acid in 
water with zinc disposed the zinc to decompose the w r ater, 
because the acid was ready to take up the oxyd as soon as 
formed. This was called a case of disposing affinity. But 
there can be no oxyd of zinc to exert this influence on the 
acid, until the water is decomposed; so that the idea that the 
acid disposed the zinc to decompose the water is quite futile. 
We find a much simpler and more probable explanation in 
the foregoing section. 

392. The recomposition or formation of water from its 
elements may be effected in a variety of ways. A mixture 
of oxygen and hydrogen gases will never unite under ordi- 
nary circumstances of temperature, &c. ; but the passage of 
an electric spark through them, or the application of red-hot 
flame, or intensely heated wire, will produce an explosive 
union, destructive to the containing vessel, unless the gas is 
in extremely small quantities. 

If this mixture is made in exact atomic proportions, and 
the gases are pure, the result of the explosion will be a com- 
plete condensation ; but usually one of the gases is in slight 
excess. 

393. This explosion may be safely made in a tube of 
very strong glass, holding only one or two cubic inches of 
the mixed gases. This tube is usually graduated into parts 
of a cubic inch, and is fitted with two wires for the passage 
of the spark, which come near to each other, but do not 
touch. A gas pistol of metal, (a,) like the figure, gives a 
perfectly safe method of performing this experiment, being 



391. What is said of disposing affinity ? 392. How is the recom- 
position of water effected ? 




COMPOUNDS OF HYDROGEN. 239 

filled with the mixed gases and stopped with a cork, (o ;) a 
smart explosion follows the passage of the spark, and the 
cork is forcibly driven out by the expansion of 
the uniting gases, accompanied by flame. 

A bladder filled with the mixed gases in 
atomic proportions, will be 4 blown into shreds 
with a deafening explosion, by the application 
tit a match to a pin-hole made in its side. Soap- 
bubbles filled from a bag of the explosive mixture 
will, from their lightness, rise rapidly, and may 
be exploded by a match or candle. In all these 
cases the sole result is the production of water ; but, being in 
the form of vapor, it escapes unseen. 

394. The formation of water may be proved by burning 
a jet of hydrogen in a dry vessel of oxygen, or even of com- 
mon air. For this purpose the jet of the compound blow- 
pipe is introduced into a large dry globe of glass, and 
the supply of the two gases regulated by the stop-cocks. 
The interior of the globe is immediately bedewed with the 
vapor of water produced in the combustion, which rapidly 
collects in drops on the sides of the vessel, and runs down 
to the bottom. No question in science has excited more 
inquiry and research, than the constitution of water. Re- 
peated trials, both analytical and synthetical, often on a most 
liberal scale and long continued, have been made to prove 
it; and the uniform result of the best experiments has been, 
that 8 parts by weight of oxygen require 1 part by weight of 
hydrogen to form 9 parts of water, and that 2 volumes of 
hydrogen saturate 1 volume of oxygen. 
j*" 395. Hydrogen is frequently employed in eudiometry, or 
^ in the analysis of gases. For this purpose a known volume 
of hydrogen is mingled with a given amount of the gas 
to be analyzed, and the mixture is exploded by electricity 
in a graduated tube of glass, or some other similar form of 
apparatus. The figure of a very good form of eudiometer 
invented by Dr. Ure, is here annexed. It is a U tube 
of stout glass ten or twelve inches long, the shorter limb of 
which is closed, and graduated into decimals of a cubic inch. 



393. How may this conveniently be done ? Name some other 
similar experiments. 394. How is the water produced in these ex- 
periments made manifest ? Describe the experiment. 395. How 
is hydrogen used in eudiometry ? 




240 NON-METALLIC ELEMENTS. 

Two wires of platinum, for the passage of 
the spark, are fused into the glass near 
the top. When it is to be used, it is filled 
with dry mercury, by placing it horizon- 
tally in the mercury trough, and a conve- 
nient portion of the mixture of the gas to 
be examined with hydrogen is then intro- 
duced. The thumb is placed over the 
open end, and by adroit management all 
the mixture is transferred to the closed 
end of the tube, and by forcing out a 
portion with a rod, thrust into the open 
end, the mercury is made to stand at the 
same level in both limbs. These adjust- 
ments being made, the whole bulk of the 
mixture is read on the graduation, and while the thumb is 
firmly held over the open end of the tube, an electrical 
spark is made to explode the gases. The air between the 
thumb and the mercury acts like a spring to break the force 
of the explosion ; and afterwards, on removing the thumb, 
the weight of the atmosphere forces the mercury into the 
shorter leg, to supply the partial vacuum occasioned by the 
union of the gases. Proper allowances being made for tem- 
perature and pressure, the quantity of residual gas is read on 
the graduation, and a calculation can then be made of the 
amount of oxygen present. If the gas contains carbon, 
cartJbnic acid would be formed, and must be absorbed by an 
alkali. 

396. The union of oxygen and hydrogen can however be 
effected slowly and quietly without any explosion, or visible 
combustion. This may be done by passing the mixed gases 
through a tube heated below redness, when combination takes 
place, without explosion. This result is accomplished at a 
still lower temperature, if the tube contains coarsely pow- 
dered glass or sand. We see in this case the operation of 
that remarkable power of surface (212) once or twice 
alluded to before ; and we will now mention a still more 
remarkable instance of the same action. 

397. Power of platinum in promoting the union of Oxy- 



Describe Ure's eudiometer. How is it used ? 396. How is the 
quiet union of hydrogen and oxygen accomplished ? 397. How does 
platinum produce this restilt ? 



COMPOUNDS OF HYDROGEN. 



241 




gen and Hydrogen. — Professor Dobereiner of Jena, many- 
years ago, (in 1824,) observed that platinum in the state of 
fine division, known as spongy platinum, would cause an 
immediate union of these ^gases. The common instrument 
employed for lighting tapers is made by taking 
advantage of this principle. A little spongy pla- 
tinum is formed into a ball, like the annexed figure, 
and mounted on a ring of wire which slips within 
the cup {d) on the top of gas-holder, (a, second 
fig.) The gas is generated by the action of dilute acid in the 
outer vessel (a) on a lump of £inc (2) hang- 
ing in the inner vessel, (f,) and is let out at 
pleasure by the cock, (c,) issuing in a stream 
on the spongy platinum. The latter is at 
once heated to redness by the stream of hy- 
drogen, which is condensed within its pores to 
such a degree that it combines with a portion 
of oxygen, always present in the sponge by 
atmospheric absorption. The union of these 
gases is always attended by intense heat, and, 
as a consequence, the platinum at once glows 
with redness, and the hydrogen is inflamed. After some 
time the sponge loses this property to a certain extent, but it 
is again restored by being well ignited. When the spongy 
platinum is mixed with clay and sal-ammoniac and made into 
balls, its effects are less intense, and such balls are often used 
in analysis to cause the gradual combination of gases. 

398. Dr. Faraday has shown, however, that it is by no 
means essential that the platinum should be in the spongy 
form in order to effect the result. Clean slips of platinum 
foil, and even of gold and pattedium, can produce the union 
of hydrogen and oxygen. For this purpose the platinum is 
cleaned in hot sulphuric acid, washed thoroughly with pure 
water, and hung in a jar of the mixed gases. Combination 
then takes place so rapidly as to cause at every instant a sen- 
sible elevation of the water in the jar. If the metal is very 
thin, it sometimes becomes hot enough during the process of 
combination to glow, or even to explode the gases. 




What common instrument illustrates this ? In what state is the 
platinum ? How is the heat produced ? 398. What has Dr. Faraday* 
shown about platinum ? How is it cleaned ? What follows its inv» 
mersion in the mixed gases ? 
21 . 



242 NON-METALLIC ELEMENTS. 

399. The same effect of platinum in causing combination 
is seen in other bodies besides oxygen and hydrogen. Sev- 
eral mixtures of carbon gases will act with platinum in the 

fsame way, and the vapors of alcohol or ether 
may be oxydized by a coil of platinum wire 
hung from a card in a wine-glass containing 
a few drops of either of these fluids. The 
coil of wire is heated to redness in a lamp, 
and while still hot is hung in the glass ; it 
then retains ifs red-hot condition as long as any 
vapor of etner or alcohol remains. In this 
case, only the hydrogen of the ether or alco- 
hol is oxydized, and the carbon is unaffect- 
ed ; a peculiar irritating ethereal odor is given off, which 
affects the nose and eyes unpleasantly. Little balls of plati- 
num sponge suspended over the wick of an alcohol lamp will 
glow after the lamp is extinguished. This is a common toy 
at the instrument- makers. 

400. Compound or oxyhydrogen blowpipe. — The heat pro- 
duced by the combustion of oxygen and hydrogen, in atomic 
proportions, is the most intense that can be obtained by 
artificial means. Dr. Hare of Philadelphia was the first who 
succeeded in forming an instrument to burn these gases 
together safely, which Professor Silliman called " the com- 
pound blowpipe." The invention was afterwards appropri- 
ated by Dr. Clark in England. The arrangement of this 
instrument is such, that the two gases are brought rrom 
separate gas-holders, by flexible tubes, so as to deliver at the 
same time two volumes of hydrogen, and one of oxygen 
gas, the hydrogen gas tube terminating in a hollow cylindri- 
cal jet, inside of which passes* the jet of oxygen gas. Thus 
arranged, the gases come in contact only at the moment of 
combustion, and all danger of explosion is avoided. 

The flame from the compound blowpipe differs from the 
common flame of a lamp or candle, by being, so to speak, an 
entire cone of ignited aerial matter, instead of being (like a 
lamp flame) ignited only on the outside ; (see flame and com- 
bustion.) Numerous modifications of the compound blowpipe 



399. What further case of surface a "ion is instanced ? 400. 
What is the compound blowpipe, and by whom invented ? How is 
it arranged? iHow does its flame differ from that of a common 
lamp? 



COMPOUNDS OF HYDROGEN. 



243. 




are in use, the most important of which we will barely men- 
tion. That most generally adopted, and the most safe, is to 
store the gases in separate holders, and bring them, as just 
mentioned, by distinct tubes to a common jet- 

401. Two bags of gum-elastic cloth answer very well to 
hold the two gases, and are fitted 
after the fashion of a bellows, with 
a hinge on one side. This is the 
mode usually adopted in the arrange- 
ment of the hydroxygen microscope. 
The effects of the compound blow- 
pipe may also be safely produced by 
passing a stream of oxygen from a 
gas-holder through the flame of a 
spirit-lamp, (20,) as is seen in the 
annexed figure. The jet is regula- 
ted by the cock, (Z,) and the lamp 
flame supplies the hydrogen. 

402. The mixed gases in atomic proportions are some- 
times forced by a condensing syringe into a very strong me- 
tallic box, from which they issue by their own 
elasticity. To prevent the danger of an explo- 
sion, a contrivance is employed called " Hem- 
ming's safety tube," which is a brass tube six 
or eight inches long, filled with fine brass 
wire, closely packed, and having a conical rod 
of brass forcibly driven into their centre, by 
which the ' wires are very closely crowded 
together. This forms in fact a great number 
of small metallic tubes, through which the gas 
must pass. It is a property of such small 
tubes entirely to arrest the progress of flame, as 
we shall see under the compounds of carbon and 
Tiydrogen. (469.) The jet is screwed to one end 
of this tube, and the other end is connected 
with the holder of the mixed gases. Several 
severe explosions, it is said, have occurred, even with all 
these precautions ; so that if the mixed gases are used at all. 




401. What arrangements are adopted for this instrument? How 
may oxygen be employed alone? 402. How are the mixed gases 
used alone ? What is Hemming's tube of safety ? 



244 NON-METALLIC ELEMENTS. 

it shorn a be only in a bag or bladder, the bursting of which 
can be attended with no danger. 

403. The effects of the compound blowpipe are very re- 
markaole. In the heat of its focus the most refractory 
metals and earths are fused, or dissipated in vapor. Plati- 
num, which does not melt in the most intense furnace of the 
arts, here fuses with the rapidity of wax, and is even volatili- 
zed. By the adroit management of the keys, which a little 
practice soon teaches, we can either reduce metallic oxyds, or 
oxydize substances still more highly. The flame of the mixed 
gases falling on a- cylinder of prepared lime, adjusted to they 
focus, produces the most intense artificial light known. This 
is sometimes called the Drummond light. It is now extensive- 
ly employed in distant night signals, and can be seen further 
at sea than any other light. Much use is also made of it as 
a substitute for the sun's light in optical experiments, which is 
a most important fact in the experimental sciences. All 
optical results can be more conveniently shown by the oxyhy- 
drogen light than by the sun ; and thus many instructive ex- 
periments can be exhibited to an evening audience, or on a 
dark day. The galvanic focus alone, among artificial sources 
of light, equals it. 

3. Natural and Chemical History of Water. 

404. Water when pure is a colorless, inodorous, tasteless 
fluid, which conducts heat and electricity very imperfectly. 
It refracts light powerfully, and is almost incapable of com- 
pression. We have made so much use of water as an exam- 
ple, in illustration of the laws of heat, &c, in the first part 
of this volume, that the reader must already be familiar with 
many of its attributes. Its greatest density, it will be remem- 
bered, (86,) is found to be at 39 0, 5, or, more exactly, 39°* 83. 
It is the standard of comparison (38) for all densities of solids 
and liquids. In the form of ice, its density is 0-92, and it 
freezes at 32°. One imperial gallon of water weighs 70,000 
grains, or just ten pounds. The American standard gallon 
holds, at 39°*83 Fahr., 58,372 American troy grains of pure 



403. What are the effects of the compound blowpipe ? What is 
the Drummond light ? What use is made of it ? 404. Give the pro- 
perties of pure water. Of what is it the standard ? How much 
does the imperial gallon hold ? How much the American ? 



COMPOUNDS OF HYDROGEN. 245 

distilled water. One cubic incrf at 60° and 30 inches baro- 
meter weighs 252*458 grains, which is 815 times as much as 
a like bulk of atmospheric air. One hundred cubic inches 
of aqueous vapor, at 212° and 30 inches barometer, weigh 
14*96 grains, and its specific gravity is 0*6202. 

405. Water boils under ordinary circumstances at 212°*, 
but we have seen (119) that its boiling point was very much 
affected by the nature of the vessel. Since the first part of 
this volume was printed we are lately informed, that water 
may be heated even to 275°, provided it be perfectly free from 
air, and that this is the case even in a vacuum. It evaporates 
at all (129) temperatures. 

406. Pure water is never found on the surface of the 
earth, for the purest natural waters contain small quanties of 
earthy or saline matters which they have dissolved from the 
rocks and soil. Moreover, all good water— that which is fit 
for the use of man — has a considerable quantity of carbonic 
acid and atmospheric air dissolved in it, and without which it 
would be flat and unpalatable. Many mineral springs, 
besides the saline matters they hold in solution, are highly 
charged with sulphureted hydrogen, carbonic acid gas, and 
other gases derived from decomposition, in the strata through 
which they pass. 

407. Pure water can be procured only by distillation, 
and it is a substance of such indispensable importance to the 
chemist, that every well furnished labratory is provided with 
means for its abundant preparation. A copper still, well 
tinned, and connected with a pure block-tin worm or conden- 
ser, answers very well to produce the common supply. But 
very accurate operations require it to be again distilled in 
clean vessels of hard glass. The solvent powers of pure 
water are in some cases much greater than of common water, 

408. The solvent powers of water far exceed those of any 
other known fluid. Nearly all saline bodies are, to a greater 
or less extent, dissolved by water, and heat generally aids this 
result. In the case of common salt, however, and a few 
other bodies, cold water dissolves as much as hot. Gases are 



What is the weight of a cubic inch of water ? 405. What is the 
boiling point of water ? What departures from this law are named ? 

406. What does common water contain ? Why is it never pure ? 

407. How is pure water obtained ? 408. How are the solvent power? 
of water ? Give examples. 

21* 



246 NON-METALLIC ELEMENTS. 

nearly all absorbed or dissolved in cold water, and some of 
them to a very great extent, while others, as hydrogen and 
common air, are very little taken up. They are all expelled 
again by boiling. Hot water dissolves many bodies which 
are quite insoluble in cold, especially when aided by small 
portions of alkaline matter. The waters of the hot springs 
in Iceland and in Arkansas deposit much silicious matter 
before held in solution ; and Dr. Turner found that common 
glass was dissolved in the chamber of a steam-boiler at 300°, 
and stalactites of silicia were formed from the wire basket in 
which the glass was suspended. This is a subject of great 
importance in many geological speculations. 

409. The powers of water as a chemical agent are very 
various and important. From its neutral, mild, and salutary 
character, we are accustomed to regard it only as a negative 
substance, possessed of little energy, while it is in fact one of 
the most important chemical agents in our possession. 
Besides its solvent powers, we know that it combines with 
many substances, forming a large class of hydrates ; hy- 
drate of lime and potash are examples. It is also, as we 
have seen, (292,) essential to the acid properties of common 
sulphuric, phosphoric, and nitric acids, acting here the part 
of a much more energetic base than in the hydrates. It 
forms an essential part in the composition of many neutral 
salts, and can be replaced in composition by other neutral 
saline bodies ; while as water of crystallization it discharges 
still another important and distinct function, the crystalline 
forms of many salts being quite dependent on its presence 
in atomic proportions. 

410. Peroxyd or Binoxyd of Hydrogen. — This curious 
P 0n ;oound was discovered in 1818 by M. Thenard. It is 
difficult °f preparation by any process ; but that lately recom- 
mended b* T -^* Pelouze is the best. It consists in decompos- 
ing the peroxyd °** barium by exactly as much very cold 
solution of hydrofiu^c acid, (fluosilicic or phosphoric acid 
may be used as well,) L* ^11 saturate the base, the whole 
being precipitated as fluorid P* barium. The reaction may 
be expressed thus : 

How does hot water act in this respect? Mention farts. 409. 
What are the powers of water as a chemical agent ? how does it 
act in sulphuric acid, &c. ? How in many salts ? 410. What w the 
peroxyd of hydrogen ? By whom, and when discovered ? How ;s it 
prepared ? 



COMPOUNDS OF HYDROGEN. 247 

Peroxyd of barium. Hydrofluoric acid. Fluorid of barium. Peroxyd of Hydrogen. 

Ba0 2 + HF = BaF + H0 2 . 

The peroxyd of hydrogen remains dissolved in the water, 
which is freed from the insoluble fluorid of barium by filtra- 
tion, and then evaporated in the vacuum of an air-pump by 
the aid of the absorbing power of sulphuric acid. 

411. Properties. — The properties of this body are very 
remarkable. When as free from water as possible, it is a 
syrupy liquid, colorless, almost inodorous, transparent, and 
possessed of a very nauseous, astringent, and disgusting taste. 
Its specific gravity is 1*453, and no degree of cold has ever 
reduced it to the solid form. Heat decomposes it with effer- 
vescence and the escape of oxygen gas. It can be preserved 
only at a temperature below 50°. The contact of carbon and 
many metallic oxyds decompose it, often explosively, and 
with evolution of light. No change is suffered by many 
bodies which decompose it ; but several oxyds, as those of 
iron, tin, manganese, and others, pass to a higher state of 
oxydation. Oxyd of silver, and generally those oxyds 
which lose their oxygen at a high temperature, are reduced 
to a metallic state by this decomposition. When diluted, and 
especially when acidulated, the peroxyd of hydrogen is more 
stable. This body is dissolved by water in all proportions, 
bleaches litmus paper, and whitens the skin. None of its 
compounds are known, nor does it seem to have any tendency 
to combine with other bodies. 

412. Ozone. — There is a remarkable body given off* 
during the electrolysis of water, having a peculiar odor, and 
very volatile. The same odor is perceived when a series of 
electrical sparks is passed through a confined portion of air ; 
and lastly, when phosphorus is slowly oxydized in a large 
volume of air, a peculiar odor is perceived, which is identical 
with the foregoing, and does not belong either to phosphorus 
or any of its compounds. This is the ozone of Professor 
Schonbein, of which much has been said in the scientific 
journals. It bleaches powerfully, and converts many pro- 
toxyds (as those of calcium and barium) to peroxyds, and 
sulphurous to sulphuric acid. It is decomposed by heat, 
water, and oxygen, like peroxyd of hydrogen ; and the latest 

Explain the reaction. 411. What are its properties ? 412. What 
remarkable body is named in connection with binoxyd of hydrogen ? 
How is it produced ? What are its properties ? What is its real 
nature ? 



248 NON-METALLIC ELEMENTS. 

opinion is, that ozone is an allotropic condition (415) of 
oxygen, analogous to the double condition of chlorine, and 
many other elements. Oa and 0/3 may be employed to ex- 
press these two states. 

4. Compounds of Hydrogen with the II. and III. Classes. 

413. The eminently electro-positive character of hydro- 
gen causes it to form well characterized and analogous com- 
pounds with all the members of the oxygen group. These 
binary compounds have frequently been called the hydracids, 
in distinction from those acid bodies already considered, 
which, in parity of language, have been called the oxacids. 

It is however more in accordance with facts and the 
principles of a philosophic classification, to look upon these 
bodies as having in reality the same essential characters as 
the chlorids, bromids, iodids, &c, of other highly electro- 
positive bases. We have already remarked, (199, note,) 
that the principles of our nomenclature require all these 
bodies to be called after their electro-negative elements, i. e. 
chlorohydric, bromohydric, &c. ; but common usage having 
established the other names, we shall not on the present 
occasion depart from them. The compounds of hydrogen 
to be considered under this head are — 

Composition by weight. 

Symbol. Hydrogen. Chlorine. 

Hydrochloric acid, HC1 1 35-41 

Bromine. 
Hydrobromic acid, HBr 1 78-26 

Iodine. 
Hydriodic acid, HI 1 126-36 

Fluorine. 
Hydrofluoric acid, HF 1 18-70 

Sulphur. 
Hydrosulphuric acid, HS 1 16-09 

Selenium. 
Hydroselenic acid, HSe 1 39-57 

Tellurium. 
Hydro telluric acid, HTe 1 64-14 

414. Action of Hydrogen with Chlorine. — These bodies 
have a very powerful affinity for each other, and combine 



413. What is said of the compounds of hydrogen with the oxygen 
group? How are the hydrac ids now looked upon ? Enumerate these, 
and give their formulas and constitution on the board. What is re- 
markable in this group ? 414. What of the affinity of chlorine and 
hydrogen ? 



COMPOUNDS OF HYDROGEN. 249 

under ordinary circumstances, when mixed in the gaseous 
state. Their affinity is such as to enable chlorine to decom- 
pose water (264) and appropriate its hydrogen. Ift^jfis way 
chlorine becomes one of the most powerful oxydizing agents 
known, since the nascent oxygen given off 'during the 
decomposition of water attacks any third body which may 
be present that is capable of combining with it. 

415. The combination of hydrogen with chlorine de- 
pends on the action of light. We have already remarked 
that light, (264,) and especially the violet ray, gives chlorine 
the power to decompose water. Chlorine prepared in the 
dark, and mingled with hydrogen, the mixture being also 
kept in the dark, will not combine with hydrogen nor decom- 
pose water, and the two bodies seem altogether indifferent 
to each other. It has been long known that the direct rays 
of the sun would cause the explosive union of this mixture ; 
and Dr. Draper has shown that chlorine gas which has been 
exposed alone and dry to the sun's light, has acquired the 
power of forming this explosive union with hydrogen, even 
in the dark, and retains it for some time. The result of this 
union is hydrochloric acid. We see in this fact the best 
proof of the double state which chlorine can assume, 
(allotropism,) and which it possesses in common with several 
other bodies. In its passive state, (as prepared in the dark,) 
it actually replaces hydrogen in the constitution of many 
organic bodies, or, in other words, assumes an electro- 
positive condition. The effect of the sun's light is to confer 
a new state upon it, probably by a new arrangement of its 
molecules, (218,) by which its character is completely 
changed. It then becomes highly electro-negative. We 
have then in chlorine an instance of an element capable of 
acting in opposite characters under different circumstances. 

416. Hydrochloric Acid, Chlorid of Hydrogen, Mu- 
riatic Acid. — This compound is formed from the action of 
dilute sulphuric acid on common salt, or chlorid of sodium. 
The reaction may be thus described : 

NaCl + S0 3 ,HO = (NaO, SO) + C1H. 
No process is more simple. A little heat is required, and 

How is it shown? How does chlorine assist in oxydation ? 415. 
On what does the combination of hydrogen and chlorine depend ? 
Explain this as illustrated. How does chlorine appear to us under 
this view ? 416. How is hydrochloric acid formed ? What other 
names has it ? 



r 



250 



NON-METALLIC ELEMENTS. 



the gas being entirely absorbed by water, must be collected 
over mercury, or in dry vessels by displacement of air. 

417. Properties. — Chlorid of hydrogen is a gas having a 
density of 1*269. It is colorless, has the greatest avidity 
for water, forms an acid fog by combining with the moisture 
of the air, which attacks the skin, has a most suffocating 
effect in respiration, and greatly irritates the eyes. It is by 
no means, however, so unpleasant as chlorine. With a 
pressure of 26*30 atmospheres, at 32°, it becomes a colorless 
liquid, which no degree of cold yet employed has solidified. 

418. This gas dissolves largely in cold water, forming 
an acid solution, which is the common muriatic acid of com- 
merce, or spirit of salt of the shops. At common tempera- 
tures water will absorb nearly 420 times its own bulk of 
muriatic acid gas. The solution is a powerful acid, of great 

use in the arts and in the 
chemical laboratory. It 
may be prepared pure by 
an arrangement of appa- 
ratus like the figure. 
The common salt is con- 
tained in a large flask 
(a) which is fitted with a 
cork having two tubes, 
one of which (b) bends 
over and dips into the 
middle bottle, (c,) which 
contains a little water to 
wash the gas. The last 
bottle (d) is filled with 
pure water, kept cool by 
ice or a freezing mixture ; 
the gas, after being wash- 
ed in the middle bottle, 
(c,) passes by the second 
bent tube (e) to the last 
bottle, where it is absorb- 
Sulphuric acid, equal in weight to the salt employed, is 
turned in successive portions upon the salt through the recurved 




417. What is its condition ? What its properties ? 418. How 
much of this gas does water absorb ? What is the solution called ? 
Explain the apparatus by which it is made. 



COMPOUNDS OF HYDROGEN. 



251 



funnel tube (f) shown on a larger«ecale in the second figure. 
This is called a safety tube ; it is bent twice on itself, and «=* 
has a ball blown on one of the turns. When a liquid " 
is poured in at the funnel-top, it must rise as high as the 
turn, before it can pass down into the flask, and a por- 
tion of the fluid is therefore always left behind in the 
bend, which serves as a valve against the entrance of 
air, and also effectually prevents an explosion of the 
flask in case the tube of delivery should become stop- 
ped. It acts also as a safety tube against the danger 
of absorption, and the rushing back of the fluid in the 
bottles by atmospheric pressure, in case the gas in the 
flask should cease to be given out. This accident, 
which not unfrequently happens, is also provided for by 
the large open tube (g) in the middle bottle through 
which the bent tube descends into the fluid, which is at the 
same time open to the air. This arrangement completely 
prevents the loss of the product in the last bottle, (d,) 
which, in case of a stoppage of the gas, would otherwise, by 
the partial vacuum resulting, be all driven back into the first 
bottle, and finally into the flask. 

The joints about the corks are made tight by a little 
yellow wax melted over them by a warm iron rod. Heat is 
applied by means of the furnace, (o,) or by a lamp. This 
same apparatus may be employed in making solutions of all 
the absorbable gases, and is so simple as to be within the 
means of the humblest laboratory ; the essential parts being 
only wide-mouthed bottles, glass tubes, a gas bottle or flask, 
and a few corks. 

419. Pure hydrochloric acid is a colorless, highly acid, 
fuming liquid, having a specific gravity of 1*2 when satu- 
rated ; it then contains 42 parts in a hundred of real acid. 
Its purity is tested by its leaving no residue on evaporating a 
drop or two on clean platinum, and by its giving no milkiness 
when a solution of chlorid of barium is added to it, [sulphuric 
acid.] Neutralized by ammonia, it ought not to become 
black when hydrosulphuret of ammonium is added, [iron.] 
It may always be obtained pure, by diluting the acid of com- 
merce until it has the specific gravity of 1*11, and distilling. 
The product is colorless and pure, having the same density. 

What is the action and use of the safety tube ? 419. What are 
the characters of pure hydrochloric acid ? How is it purified ? 



252 NON-METALLIC ELEMENTS. 

The commercial acid is always impure, and colored yellow 
by free chlorine, iron, and organic matters. A solution of 
nitrate of silver detects the presence of a soluble chlorid, or 
of hydrochloric acid, by forming with it a white curdy pre- 
cipitate of chlorid of silver, which is soluble in ammonia, but 
insoluble in acids or water. This acid is an electrolyte, 
(236, 1,) and is also decomposed by ordinary electricity. A 
mixture of muriatic acid gas with oxygen, passed . through a 
red-hot tube, produces water and chlorine. 

420. The uses of hydrochloric acid are very numerous. 
Its decomposition by oxyd of manganese affords the easiest 
mode of procuring chlorine. It dissolves a great number 
of metals forming chlorids, from which these metals may be 
obtained in their lowest state of oxydation. In chemical 
analysis and the daily operations of the laboratory it is of 
indispensable use. Mingled with half its own volume of 
strong nitric acid, it makes the deeply-colored, fuming and 
corrosive aqua regia. This mixed acid evolves much free 
chlorine, which in its nascent state has power to dissolve 
gold, platinum, &c, forming chlorids of those metals, and 
not nitromuriates, as was formerly supposed. As soon as 
all the chlorine is evolved, this peculiar power of the aqua 
regia is lost. 

421. Hydrochloric acid is made in the arts in immense 
quantities, especially in England, where the carbonate of 
soda is largely made from common salt, (chlorid of sodium,) 
by the action of sulphuric acid. The vast volumes of chlorid 
of hydrogen which are evolved in this process, are by law 
required to be condensed, to avoid the injury to vegetation 
and health formerly experienced, from their being allowed to 
escape into the atmosphere. In this way, hydrochloric 
acid is made as an incident to other processes, in such quan- 
tities as to overstock the market. 

422. Hydrobromic Acid — Bromid of Hydrogen. — Hy- 
drogen and bromine do not act upon each other in the 
gaseous state, even by the aid of the sun's light ; but a red 
heat or the electric spark causes union, — only among those 
particles, however, which are in immediate contact with the 
heat, the action not being general. Hydrobromic acid may 



What impurities have the commercial acids ? How are they de- 
tected ? 420. What are its uses ? What is aqua regia ? What use 
has it, and on what dependent ? 421. What is said of the abundance 
of this acid ? 422. How do hydrogen and bromine act together? 



COMPOUNDS OF HYDROGEN. 253 

be prepared by the reaction of moist phosphorus on bromine 
in a glass tube. The gas given off must, be collected over 
mercury. It is composed, like hydrochloric acid, of equal 
volumes of its elements not condensed. Its specific gravity 
is 2*731, and it is condensed by cold and pressure into a 
liquid. In its sensible properties it bears a close resemblance 
to hydrochloric acid. With the nitrates of silver, lead, and 
mercury, it gives white precipitates similar to the chlorids. 
It has a strong avidity for water, and dissolves largely in it, 
giving out much heat during the absorption. The saturated 
aqueous solution has the same reactions as the dry acid, and 
fumes with a white cloud in contact with air. It dissolves a 
large quantity of free bromine, acquiring thereby a red tint. 

423. Hydriodic Acid — Iodid of Hydrogen. — This body 
may be formed by the direct union of its elements at a red 
heat, but is more-ffe'asily prepared by acting on iodine and 
water with phosphorus, by which means the gas is given out 
in large quantities. The action of phosphorus and iodine is 
violent and dangerous, but may be regulated and made safe 
by putting a little powdered glass between each layer of 
phosphorus and iodine. Phosphoric acid is formed and 
remains in solution, while the 
hydriodic acid gas is given out, and 
may be collected over mercury, or 
dissolved in water. The dry gas 
has a great avidity for water. Its 
specific gravity is 4-385, air = 1 ; 
being formed like the two last of 
one volume of each element uncon- 
densed. Cold and pressure reduce 
it to a clear liquid, which, at — 60° Fahr., freezes into a 
colorless solid, having fissures . running through it like ice. 
It forms a very acid fluid by solution in water, which has, 
when saturated, a specific gravity of 1*7, and emits white 
fumes. 

The aqueous solution is also prepared by transmitting a 
current of hydrosulphuric acid through water in which free 
iodine is suspended. The gas is decomposed, sulphur set 

How is hydrobromic acid prepared ? What character has it ? 423. 
How is hydriodic acid prepared ? What is the reaction ? What are 
the properties of the gas ? How else may the aqueous solution be 
prepared ? 

22 




254 NON-METALLIC ELEMENTS. 

free, and hydriodic acid produced, which is purified from 
free hydrosulphuric acid by boiling, and from sulphur by 
filtration. 

424. The aqueous hydriodic acid is easily decomposed 
by exposure to the air, iodine being set free. It forms 
characteristic, highly colored precipitates with most of the 
metals, particularly with lead, silver, and mercury. Bro- 
mine decomposes it, and chlorine decomposes both hydrc- 
bromic and hydriodic acids, thus showing the relative 
affinities of these bodies for hydrogen. This acid is a 
valuable reagent ; its presence in solution is easily detected 
by a cold solution of starch with a few drops of strong nitric 
or sulphuric acid, which instantly gives the fine charac- 
teristic blue of the iodid of starch. 

425. Hydrofluoric Acid, or Fluorid of Hydrogen, is 
obtained from the decomposition of fluor-spar by strong sul- 
phuric acid. The operation must be performed in a retort 
of pure lead, silver, or platinum, and requires a gentle heat. 
The fluorine leaves the lime and joins the hydrogen of an 
atom of water in the acid, forming hydrofluoric acid, while 
sulphate of lime remains behind ,* or, expressed in symbols, 

Fluorid of Sul. acid. Sul. lime. Fluorid of 

calcium. hydrogen. 

CaF + S0 3 , HO = S0 3 , CaO + HF 

The fluor-spar must be pure, and especially free from silica. 

426. Properties. — Hydrofluoric acid is a gas which at 
32° is condensed into a colorless fluid, with a density of 
1*069, which can be preserved as a fluid even at higher 
temperatures in well stopped bottles of silver or lead. Its 
avidity for water is extreme, and when brought in contact 
with it, the acid hisses like red-hot iron. Its aqueous 
solution, as well as the vapor of the acid, attacks glass very 
powerfully, and is often used to etch it, as, for example, in 
marking the test bottles in the laboratory, or biting in 
designs traced in wax on the surface of glass plates. IHs a 
powerful acid, with a very sour taste, neutralizes alkalies, 



424. What properties has the aqueous hydriodic acid ? What are 
the mutual relations of iodine, bromine, and chlorine, as shown by 
their compounds with hydrogen ? How is the presence of hydriodic 
acid detected ? 425. What is hydrofluoric acid ? Explain the reac- 
tion by which it is produced. 426. What are the properties of this 
body ? What is its most remarkable affinity ? 



COMPOUNDS OF HYDROGEN. 255 

and permanently reddens blue litmus. On some of the 
metals its action is very powerful ; it unites explosively with 
potassium, evolving heat and light. It attacks and dissolves, 
with the evolution of hydrogen, certain bodies which no othei 
acid can affect, such as silicon, zirconium, and columbium. 

Silicic, titanic, columbic, and molybdic acids are also 
dissolved by it. 

427. Hydrofluoric acid is a most dangerous body to 
experiment with. It attacks all forms of animal matter with 
wonderful energy. The smallest drop of the concentrated 
acid produces ulceration and death, when applied to the 
tongue of a dog. Its vapor floating in the air is very corro- 
sive, and should be carefully avoided. If it falls, even in 
small spray, on the skin of the hand or any part of the body, 
it produces a malignant ulcer, which it is very difficult to cure. 
Any considerable quantity of it would prove fatal. For this 
reason it is quite inexpedient for unexperienced persons to 
attempt its preparation. By using a weaker sulphuric acid, 
however, and having water in the condenser, no risk is 
incurred. As before remarked, it attacks silica more pow- 
erfully than any other body, and their mutual affinity is one 
of the most powerful known to us. This fact puts us in 
possession of an admirable mode of analyzing silicious min- 
erals, when we do not wish to fuse them with an alkali. By 
exposing the fine powder of the moistened mineral to the 
vapor of the hydrofluoric acid, all the silica is taken up and 
carried away as hydrofluosilicic acid gas, (364. f 

428. The hydrofluoric acid was formerly called fluoric 
acid, and the fluor spar, a fluate of lime. We now know 
that this mineral is a fluorid of calcium, in exact analogy 
with the chlorid of sodium, and a very numerous class of 
similar binary compounds, with which our study of the metals 
will familiarize us. 

429. Hydro sulphuric Acid — Sulpkureted Hydrogen. — 
When the protosulphuret of iron or the sulphuret of antimony 
is treated with a dilute acid, effervescence occurs, and a gas 
is given out having a most disgusting fetid odor, which at 
once reminds us of the nauseous smell of bad eggs. This 

What are its relations to the metals ? What acids are dissolved 
by it? 427. How does it affect animal matter? What caution is 
given ? What analytical use is named for this acid ? 428. What 
was this acid formerly called ? What more exact knowledge do we 
now possess ? 429. What is hydrosulphuric acid, and how set free ? 



* 



256 NON-METALLIC ELEMENT9. 

is sulphureted hydrogen gas, one of the most useful reagents 
to the chemist, especially in relation to the metallic bodies. 

430. Properties. — This gas is colorless, and less offensive 
in quantity than when the air is contaminated with only a 
t»"ace. It burns with a pale blue flame like that of sulphur, 
water and sulphurous acids being the products. If oxygen is 
mingled with it, and the mixture ignited, or touched with a 
match, it explodes with a shrill sound, sulphur is deposited, 
and water formed. When the oxygen is in the proportion of 
150 measures to 100 of sulphureted hydrogen, the combus- 
tion is complete, and only sulphurous acid and water are 
formed. Strong nitric acid and chlorine gas also decompose 
it, and sulphur is set free. It has a specific gravity of 1*1 71, 
and 100 cubic inches of it weigh 36*33 grains. At a tem- 
perature of 50°, it is made liquid by a pressure of 14-5 
atmospheres, and at —122° Fahr., it freezes into a white 
confused crystalline solid, not transparent, and which is 
much heavier than the fluid, sinking in it readily. 

431. Cold water dissolves its own volume of sulphureted 
hydrogen, and acquires its peculiar odor and properties. 
When recently prepared, it takes the place of the gas as a 
test ; but it is so easily decomposed by contact with the air, 
with the deposition of sulphur, that it cannot long be kept on 
hand. 

The student should always have at hand in the laboratory 
a little gas bottle, like the figure, holding 
some fragments of protosulphuret of iron, 
to which, when the gas is wanted, a little 
water is added and then a few drops of 
oil of vitriol. Effervescence ensues, and 
the gas is delivered by the bent tube, 
into any solution which we desire to treat 
with it. 

432. Properties and Uses. — This gas posesses the pro- 
perties of an acid ; its aqueous solution reddens litmus paper, 
and it forms compounds with many bases. It precipitates 



What other name has it ? 430. What are its properties ? How 
does it smell ? Is it combustible ? How does it burn when mingled 
with oxygen ? Is it condensable to a fluid ? 431. How much of it 
will water dissolve ? What properties has the solution ? What ob- 
jection to its use ? What mode is preferred for using this reagent ? 
432. How is it seen to be an acid ? What are its properties and 
uses? 




COMPOUNDS OF JJYDROGEN. 



257 



from solution all the metals whose sulphurets are insoluble in 
water, often giving the most characteristic precipitates. It 
thus enables the chemist to effect many separations of metals 
with ease and certainty, and, as before remarked, is one of 
his most valuable reagents. Its presence in solution is at 
once detected by its blackening the salts of lead. Characters 
drawn on paper with a solution of the acetate of lead, are quite 
colorless ; but a stream of sulphureted hydrogen at once 
causes them to stand forth in deep black, its action producing 
the dark sulphuret of lead. 

433. It occurs in solution in many mineral springs, giving 
the water highly valuable medicinal characters. Such springs 
are much resorted to in this country, as at Avon, N. Y., and 
the sulphur springs of Virginia. The disgust at first felt at 
drinking these, nauseous waters is soon overcome, and those 
patients who take them in large quantity soon observe 
the gas to penetrate their whole system and exude in their 
perspiration. Silver coin, and other silver articles in the 
pockets of such persons are soon completely blackened by the 
coating of sulphuret of silver formed on their surface. 

434. Although salutary when used in the stomach, it has 
been found to be a deadly poison to the more-delicate animals, 
even when present in the air in only a small quantity. The 
operative chemist is, however, in the habit of breathing it 
with impunity, for the atmosphere of an active laboratory is 
often impregnated with it, 

435. When sulphurous r *\ /A 
acid and sulphureted hy- f^^ 5 ^ - ~ 
drogen gas are brought 
together in a common re- 
ceiving vessel, mutual de- 
composition ensues, and 
the sulphur of both is 
thrown down in a yellow 
cloud, which attaches it- 
self to the sides of the 
vessel. The same ar- 




How does it act with the metals ? How is its presence detected ? 
433. How does this gas occur in nature ? What use is made of sul- 
phureted waters ? 434. What is said of the effect of this gas on the 
system of animals ? 435. What is the reaction when sulphuric acid 
and hydrosulphuric acid gases are mingled I 
22* 



258 NON-METALLIC ELEMENTS. 

rangement of apparatus which was employed for illustrating 
the formation of sulphuric acid, will answer in this experi- 
ment, substituting the materials for sulphureted hydrogen in 
the flask, (b.) 

436. Hydrpselenic Acid — Seleniureted Hydrogen. — 
This body is quite similar to the foregoing, and is formed in 
the same manner by decomposing the protoseleniuret of any 
of the more easily oxydized metals, with a weak acid. Its 
properties and reactions are very similar to those of the 
hydrosulphuric acid. It is absorbed by water, turns the skin 
brown, and irritates the mucous membrane. 

Tellureted Hydrogen is evolved when an alloy of tin 
and tellurium is acted on by muriatic acid: it reddens lit- 
mus paper, dissolves in water, and possesses the general 
habitudes of sulphureted hydrogen. 

5. Compounds of Hydrogen with Class III. 

437. The compounds which hydrogen forms with the nitro- 
gen group, are strongly contrasted in chemical and physical 
characters with the remarkable natural family which has 
just engaged our attention. The latter are all acid, and gen- 
erally in an eminent degree. The compounds of hydrogen 
with the nitrogen group are, on the contrary, either neutral 
or strongly basic, forming a series of salts or peculiar com- 
pounds with the hydracids before named ; thus furnishing a 
strong reason for the propriety of the arrangement which we 
have adopted in our classification. 

The compounds named under this head, are — 

Composition by weight. 

Symbol. Nitrogen. Hydrogen. 
Ammonia, NH 3 14-06 3 

Phosphorus. 
Phosphureted hydrogen, PH 3 31-38 3 

438. Ammonia, and the other compounds of nitrogen and 
hydrogen, might with propriety be treated under organic 
chemistry, since hydrogen and nitrogen do not, by any 

436. What is hydroselenic acid, and how allied to the last body ? 
437. What is said of the compounds of the hydrogen with the nitro- 
gen group ? What compounds are named ? Give their symbols and 
composition. 438. Where might ammonia be more properly 
treated of ? 



COMPOUNDS OF HYDROGEN. 259 

direct means, unite as gases, and all the compounds of am- 
monia may ultimately be traced back to an organic origin. 
Ammonia is almost invariably one of the products of the 
decomposition of those organic matters which contain nitro- 
gen ; and we shall see, when we come to study these bodies, 
that their elements are so arranged, that we might expect such 
a result. Ammonia is however so important a body in relation 
to the metals, and, in fact, as a reagent in nearly all chemical 
experiments, that we shall find it more convenient to become 
acquainted with it here, than at a later period of our studies. 

439. History. — Sal ammoniac and the watery solution 
of ammonia have been long known, and probably were in 
use among the ancients. The very name of ammonia indi- 
cates its antiquity.* The sal-ammoniac, sulphate of ammo- 
nia, and ammonia-alum are found among the products of 
volcanoes. Free ammonia is exhaled from the foliage and 
found in the juices of certain plants, in the perspiration of 
animals, in iron rust and absorbent earths. Rain water also 
contains a small quantity of ammoniacal salts, washed out of 
the atmosphere ; and the guano so much valued as a manure, 
is rich in various ammoniacal compounds. 

440. Preparation. — Ammonia is best prepared for use 
by decomposing one of its saline compounds, as the sal-am- 
moniac, by an alkali and heat. For this purpose equal parts 
of dry powdered sal-ammoniac and freshly slaked dry lime 
are well mingled and heated in a glass, or if the quantity is 
considerable, in an iron vessel. The lime takes the hydro- 
chloric acid, forming a chlorid of calcium, and ammonia is 
given out as a gas. 

441. Properties. — The dry gas is colorless, having the 
very pungent smell so well known as that of ' hartshorn. 1 
It is, when undiluted, quite irrespirable, and attacks the eyes, 
mouth, and nose powerfully. It is alkaline, and has fre- 
quently been called the volatile alkali. Being very rapidly 
absorbed by water, it must be collected over mercury or in 

439. What is known of the antiquity of ammonia? What ammo- 
niacal compounds are found native ? What other natural sources of 
ammonia are named ? 440. How is ammonia prepared ? 441. 
What are the properties of this gas ? 

* From Ammon, an epithet by which Jove was known, and ammos, 
sand, in allusion to the Egyptian desert of Ammon, where sal-ammo- 
niac was first obtained. 



260 



NON-METALLIC ELEMENTS. 



inverted dry vessels. It does not support the combustion of 
a candle, and does not burn itself, although a small jet of the 
gas will burn in pure oxygen, and the flame of the candle, as 
it goes out, is slightly enlarged with a yellowish fringe. 
Mixed with an equal volume of oxygen, it explodes with the 
electric spark, yielding water and free nitrogen. The dry 
gas passed through a red-hot tube is completely decomposed ; 
200 measures of the gas yielding 400 measures after decom- 
position, which by analysis is found to consist of 300 measures 
of hydrogen and 100 of nitrogen. The specific gravity of 
dry ammonia is therefore (192) 0*5898, and 100 cubic 
inches weigh 18-28 grains. By pressure it is easily con- 
verted into a liquid, which freezes at — 103° Fahrenheit, 
producing a white translucent crystalline solid, which is 
heavier than the liquid. 

\ 442. The solution of this gas in water (called aqua am- 
monice, and sometimes improperly liquid ammonia) is easily 
prepared, and possesses all the peculiar properties of the gas. 
This is best made by an arrangement like the annexed figure, 
called Woulfe's apparatus. This consists essentially of the 
gas bottle (a,) which contains the materials to generate the 
gas, and is placed over a furnace. Three three-necked bot- 
tles (b c d) are all connected with a by a series of bent tubes, 
(i i i i). The gas in passing from a by i, must go through 
a portion of water in b, where it is absorbed. It is prevented 
from escaping by a tube in the middle orifice, (o,) which has 




its lower end dipping a little way into the water of each 
bottle. The effect of this is to cause a column of liquid to 



How does it affect combustion ? How is it analyzed ? What is 
its constitution by weight and volume ? What is its density ? How 
does cold affect it? 442. How is aqua ammoniae prepared? Ex- 
plain Woulfe's apparatus and its mode of action. 



COMPOUNDS OF HYDROGEN. 261 

play up and down in o, as the pressure of the gas varies. 
Each tube, (i) has a shorter end not reaching the fluid. 
Things being thus arranged, and the tightness of all the joints 
and corks being secured by bees-wax, the gas bubbles through 
b y until the water can absorb no more ; it then passes on to 
c, and then to d, saturating each in turn. In the last vessel 
is a little mercury under which the bent tube (i) dips, with 
the design of creating a slight pressure on the whole appa- 
ratus, as is indicated by the height of the column of water in 
ooo. It only remains to keep the whole (b c d) cold, and 
the water in the bottles will then soon become saturated with 
the gas. The first bottle is usually contaminated by foreign 
matters, and is rejected. Under sulphuret of ammonium 
will be found a more simple form of the same apparatus 
formed of common wide-mouthed bottles. 

443. The saturated aqueous solution of ammonia has a 
specific gravity of about 0-875, is colorless and transparent, 
and exhales the gas abundantly ; when it is of this density it 
contains 32 per cent, of real ammonia. It must be kept in 
tight bottles, to prevent the loss of strength and the absorp- 
tion of carbonic acid gas from the air. It has all the charac- 
ters of an alkali, it saturates the most powerful acids, and 
forms a series of salts which are all soluble in water, and are 
volatilized at a red heat. It boils vehemently at 130°, and 
freezes at about 40° below zero. It browns yellow turmeric 
paper temporarily, but the original color returns as the gas 
evaporates. 

444. The presence of ammonia is always recognised by 
its odor, by its action on turmeric or blue cabbage paper, 
(which last it turns green,) and especially by the white cloud 
of muriate of ammonia which is formed on bringing a rod 
moistened with hydrochloric acid near it. 

445. Hydrogen and Phosphorus — Phosphureted Hy- 
drogen. — This gaseous body is formed when the phosphuret 
of calcium, or of some other alkaline metal, is acted upon by 
water ; but is more conveniently prepared by employing 
quick-lime recently slaked, water, and a few sticks of phos- 
phorus, in a small retort, the ball of which is nearly filled 
with the mixture. A gentle heat generates the gas, which 

WTiat properties ? 443. What gravity has the saturated aqueous 
solution? What characterizes its salts? 444. How is ammonia 
recognised ? 445. What is phosphureted hydrogen, and how prepared ? 



262 



NON-METALLIC ELEMENTS. 



breaks from the surface of the water (beneath which the 
beak of the retort dips very slightly) in bubbles, that inflame 




i fi lf llilni l Hnl l i.iiBmnM I Ul X Wl—Hy 



spontaneously as they reach the air, rising in beautiful 
wreaths of smoke, which float in concentric, expanding rings 
This gas loses its spontaneous inflammability by standing a 
time over water, a body not yet obtained in a separate form 
being deposited. A few drops of ether or oil of turpentine 
destroy this property, but a very little nitrous acid restores it. 

446. Properties. — This gas has a disgusting, heavy 
odor, like putrid fish, which is far more annoying than sul- 
phureted hydrogen. It is transparent and colorless, has a 
bitter taste, and if dry may be kept unchanged either in the 
light or dark. It is deadly when breathed. When procured 
as just described, it acts very violently with oxygen gas. 
If bubbles of it are allowed to enter a jar of oxygen, each 
bubble burns with a most brilliant light and a sharp ex- 
plosion. The mixture of even a very small quantity with 
oxygen would be quite hazardous. 

447. Phosphureted Hydrogen is neither alkaline nor 
acid, but it has more resemblance to an alkali than to an acid, 
since it forms, with several metallic chlorids, compounds 
analogous to those which ammonia yields with the same 
bodies. It also combines with hydrobromic and hydriodic 
acids, forming colorless crystalline salts, which are decom- 
posed by water. 

448. Three Pkosphurets of Hydrogen have been distin- 
guished, which have the formulas PH, PH 2 , and PH 3 . The 



What remarkable property has the fresh gas ? Is this property 
constant ? 446. What are its characters ? How does it react with 
oxygen ? 447. Is this gas alkaline or acid ? What compounds 
analogous to salts does it form ? 448. How many and what phos- 
phurets of hydrogen are known ? 



7 



\ 



COMPOUNDS OF HYDROGEN. 263 



L 

last is the pure gas, the second is the spontaneously in- 
flammable body, and the first is a solid. 

6. Compounds of Hydrogen with the Carbon Group. 

449. Carbon and hydrogen unite to form a vast number 
of compounds, all of which, directly or indirectly, are the 
product of organic life, and will therefore (with two excep- 
tions) be discussed more properly in the organic chemistry. 

450. The carbo-hydrogens, as these bodies are often 
called, are sometimes solids at common temperatures, as 
paraffine and nephthaline ; or liquids, as the oils of turpen- 
tine, lemons, and naphtha. Two of them are gases, and 
being also products of the mineral kingdom, they may be 
properly discussed under inorganic chemistry. We refer 
to the 

Composition by weight. 



Symbol. Carbon. Hydrogen. 

Light carbureted hydrogen gas, CH2 6 2 
defiant, or heavy carbureted 

hydrogen gas, C2H2 12 2 

451.. Light Carbureted Hydrogen Gas; Marsh Gas, 
Fire Damp ; or Di-carburet of Hydrogen. — This gas occurs 
abundantly in nature, being formed nearly pure by the 
decomposition of vegetable matter under water. The bubbles 
which rise, when the leaves and mud of a stagnant pool or 
lake are stirred, are light carbureted hydrogen, with about 
Jq- of carbonic acid. It is also evolved in large quantity in 
coal mines, but is then accompanied by several other gases. 
fn the salt regions of this country it is given out abundantly 
with defiant gas from some of the artesian wells bored for 
salt water. It is also sometimes blown out in a strong blast 
from fissures in the earth ; and it forms a part of the gas 
employed to light cities, 

452; Preparation.— This gas may be prepared artificially 
by mixing equ>il parts of acetate of soda, and solid hydrate 



449. What is said of the number and nature of the compounds of 
carbon and hydrogen? Of what are they the product ? 450. How 
do the carbo-bydrogens present themselves ? What two are 
referred to? Give their* formulas and composition. 451. What 
other names has the light carbureted hydrogen ? What natural 
supplies have we of it ? 452. How is it prepared ? 



264 NON-METALLIC ELEMENTS. 

of potash, with one and a half parts of quicklime. The mix- 
ture is strongly heated in a retort, when the gas, perfectly- 
pure, is disengaged abundantly, and may be collected over 
water. The hydrate of potash decomposes the acetic acid at 
a high heat, and takes from it two equivalents of carbonic 
acid, while two equivalents of marsh gas are given off; 
thus: 

Acetic acid, C 4 H 3 3 ) ( Carbonic acid, 2 eq C 2 4 

Water, HO (~) Marsh gas, 2 eq C 2 Hi 



C 4 H 4 4 C 4 H4 4 

The use of the lime is to keep the potash from acting on the 
glass retort. 

453. Properties. — This gas has a density of *5595, and 
100 cubic inches of it weigh 17.41 grains. It is composed 
of one volume of carbon and two volumes of hydrogen, or 
six parts by weight of the former to two of the latter. It is 
neutral, inodorous, tasteless, and respirable without poison- 
ous effects. Water absorbs very little of it, and it has not 
been condensed into a liquid. Twice its bulk of oxygen 
burns it completely, with a loud explosion, forming water 
and an equal volume of carbonic acid. In the air it burns 
quietly with a bright yellow flame, giving the same products. 
It is not easily decomposed ; but at a red heat, in a porce- 
lain tube, it deposits carbon and gives out hydrogen. With 
moist chlorine in the sun-light, it forms carbonic and hydro- 
chloric acids, but is not affected by it in the dark-. 

454. Olejiant Gas, or heavy Curbureted Hydrogen Gas. 
— This gas was discovered in 1796, by an association of 
Dutch chemists, who gave it the name of olefiant, because it 
forms a peculiar oil-like body with chlorine. It is prepared 
by mixing strong alcohol with five or six times its weight of 
oil of vitriol in a capacious retort, and applying heat to the 
mixture. The action is complicated and cannot be well 
explained at this time. Ether distils over soon after the heat 
is applied, and with it, the olefiant gas which may be collect- 
ed over water. The alcohol becomes carbonized, froths up 
very much, and carbonic and sulphurous acids are given off 

Give the reaction. 453. What is the density and composition of 
this gas? Give its general properties. How does it act with 
chlorine. 454. When, and by whom, was olefiant gas discovered ? 
Whence its name ? How is it prepared ? What is the result ? 



COMPOUNDS OF HYDROGEN. 265 

towards the close of the process. The*gas can be purified by 
passing it first through a wash-bottle containing a solution 
of potash, and then through oil of vitriol ; the potash 
removes the acid vapors, and the oil of vitriol retains the 
ether. 

455. Properties. — Olefiant gas is a neutral, colorless, 
tasteless gas, nearly inodorous, and having a density of 
0*981, 100 cubic inches of it weighing 30*57 grains. It 
burns with a most brilliant white light, and evolves much free 
carbon. Its splendid combustion makes it a favorite subject 
of experiment. With an equivalent quantity of oxygen 
gas, it explodes with a tremendous detonation, which is too 
severe even for very strong glass vessels. Bubbles of the 
mixture may be exploded by a burning paper, as they rise 
from beneath the surface of water. It is decomposed by 
passing through tubes heated to redness, and much carbon is 
deposited. This effect happens in the irou retorts of city 
gas works, in which crusts of pure carbon, sometimes of 
great thickness, accumulate from the decomposition of the 
gas. 
Xy 456. As already remarked, this gas forms a remarkable 
compound with chlorine ; the gases unite (2 volumes of 
chlorine and 1 of olefiant) by simple contact, the dense oily 
liquid collects on the side of the air-jar and surface of the 
water, and may be received as it falls in a basin placed for 
the purpose under the jar. 

If two measures of chlorine and one of olefiant gas be 
fired as soon as the mixture is made, by a candle, or lighted 
match, from the open mouth of the jar, the hydrogen of the 
olefiant unites with the chlorine, and all the carbon of the 
former is set free in a dark cloud, filling the vessel. 

457. Coal gas and resin gas are much used for illumi- 
nating cities ; they are formed chiefly of light carbureted hy- 
drogen and olefiant gas, with some other volatile hydrocar- 
bons. Their illuminating power is in proportion to the 
amount of olefiant gas contained in the mixture. Numerous 
products from the destructive distillation of coal and resin 

455. What properties has olefiant gas ? How does it burn ? How 
does it act with oxygen ? How is it decomposed ? What happens 
in large gas retorts ? 456. How does olefiant gas act with chlo- 
rine ? If the mixture is at once fired, how does it act ? 457. For 
what are coal and resin gases used ? On what depends their illumi- 
nating power ? 
23 



1 ■■■ 



266 NON-METALLIC ELEMENTS. 

require to be removed before the gas is fit for use. It is 
accordingly washed in milk of lime to free it from sulphu- 
reted hydrogen and carbonic acid, and sometimes with dilute 
sulphuric acid to remove ammonia. Tar and soluble oils are 
condensed by passing the gas through a series of iron pipes 
in water, which is done before it goes to the lime purifiers. 
The gas from oil has a higher illuminating power, and needs 
no purification when well prepared. 

A natural supply of coal gas, composed of light carbureted 
hydrogen and defiant gas, is used to illuminate the village of 
Fredonia, N. Y. ; and some of the salt works in Kenawha, 
Va., are heated by the burning gas conducted for the purpose 
under the kettles. Vast volumes of this gas are given off 
from the Artesian borings in those regions. 

458. Hydrogen combines with boron, forming a combus- 
tible gas, which burns with the green flame peculiar to the 
compounds of boron, and deposits boracic acid. Its compo- 
sition and properties are not known. From analogy we 
might suspect the existence of a series of borurets of hydro- 
gen, and possibly siliciurets of the same element. 

7. Combustion and the Structure of Flame. 

459. Combustion is the disengagement of light and heat, 
which accompanies chemical combination. Nearly all our 
operations being performed in presence of the oxygen of the 
atmosphere, the term combustion has come to be restricted, 
in a popular sense, to the union of bodies with oxygen, when 
heat and light are accompaniments of such union. 

Combustible bodies, in the common sense of the term, are 
those which burn (z. e., unite with oxygen with heat and 
light) under ordinary circumstances. Thus, carbon, sulphur, 
and phosphorus, are among the elementary combustibles ; 
and tar, oils, wood, &c, are compound combustibles. 
Oxygen being possessed of stronger affinities than any other 
elementary body, forms compounds with those bodies which 
are burned in it, which are no longer combustible ; thus iron 
which has been burnt (i. e. oxydized) in oxygen gas, (255,) 

How are they purified ? What natural supplies of coal gas are 
named ? 458. What compound of hydrogen and boroa is named ? 
459. What is combustion ? What popular restriction has arisen in 
the use of this term ? What is commonly meant by combustible 
bodies ? What is said of bodies which have been burnt in oxygen ? 



COMBUSTION AND FLAME. 267 

is no longer capable of a similar change, because we have 
no other body, which, at common temperatures, can remove 
the oxygen from combination. Iron will also burn brilliantly 
in sulphur vapor, forming a compound, (protosulphuret of 
iron,) which is incombustible in an atmosphere of sulphur 
vapor, but which will still burn in oxygen gas. This is only 
saying that the affinities (i. e. the electro-negative qualities) 
of oxygen are more powerful than those of sulphur. 

460. The division of elementary bodies into combustibles 
and supporters of combustion, was proposed by Doctor 
Thomson, and that classification has prevailed with English 
and American authors to a great extent. This principle is 
radically defective as a guide to any philosophical arrange- 
ment of bodies, since it seizes on a single phenomenon ac- 
companying chemical union, and disregards most of those 
natural analogies which group the elements into distinct 
classes. 

It has been remarked by an old writer on chemistry, that 
" combustion is the grand phenomenon of chemistry." It 
would be more conformable to truth to say, that affinity is 
the grand phenomenon of chemistry, and that its exertion is 
sometimes accompanied by the evolution of heat and light. 

The attentive student has already, it is hoped, found 
sufficient grounds, in the arguments and illustrations which 
have been presented, to admit the existence of a higher 
chemical philosophy than that of combustibles and sup- 
porters. 

461. In all cases of combustion the action is reciprocal. 
Hydrogen burns in common air ; but if a stream of oxygen 
is thrown into a jar of hydrogen, through a small aperture at 
the top, when the latter is burning, the flame is carried down 
into the body of the jar, and the oxygen will continue to 
burn in the hydrogen, as it issues from the jet. In this 
case the oxygen may be said to be the combustible, and the 
hydrogen the supporter. The simple statement in both 
cases is, that oxygen and hydrogen combine together, and 
combustion — that is, the disengagement of light and heat — 

Illustrate this. 460. What is said of the division of bodies into 
combustibles and supporters of combustion? Why is this principle 
of classification radically deficient? 461. What is said of the re- 
ciprocal action of combustion ? Illustrate this by a jet of oxygen 
in hydrogen gas. 



268 NON-METALLIC ELEMENTS. 

is the consequence.* The diamond burns in oxygen gas ; 
but the latter is as much altered by the union as the former, 
and we cannot therefore say whether the oxygen or the 
carbon is the most burnt. Heat and light attend this union ; 
but the carbon of the human body is as truly burnt in the 
lungs by the atmospheric oxygen, as is the fuel of our fires ; 
and the product of the combustion, the carbonic acid 
thrown out by the lungs at every exhalation, is the same 
thing which is discharged at the mouth of a furnace. In the 
case of the animal body, the combustion is so slow that no 
light is evolved, and only that degree of heat (98° to 100°) 
which is essential to vitality. We cannot deny that there is/ 
in this case a real combustion, and yet it does not answer to 
our usual definition, since no light is evolved. The term 
combustion must have, then, a chemical sense vastly more 
comprehensive than its popular meaning. The rust which 
slowly corrodes and destroys our strongest fixtures of iron, 
and the gradual process of decay which reduces all structures 
of wood to a black mould, are to the chemist as truly cases 
of combustion, as those more rapid unions with oxygen 
which are accompanied by the splendid evolution of light and 
heat. 

462. The heat produced by combustion has received no 
satisfactory explanation. All we can say is, that any change 
of state in a body is accompanied by an alteration of tem- 
perature. When two liquids become solid, we can better 
understand why heat should be produced, (109.) But why 
the union of carbon and oxygen, to form a gas, should evolve 
such intense heat as to fuse the most refractory bodies, is 
more than has been explained. It will be remembered that 
chemical combination was pointed out as one of the sources 
of heat, and that it is strictly limited to the amount of matter 
suffering change. 

463. The temperature at which bodies become luminous 
in diffuse daylight is considered to be about 1000°. Gases, 
however, can be heated much higher without being luminous ; 

The burning of the diamond. What is said of those cases where 
no light or heat accompanies the change ? 462. How is the heat 
of combustion explained ? 463. At what temperature do bodies 
become luminous ? How is it with gases ? 

* Daniell's Introduction to Chemical Philosophy, p. 322. 



COMBUSTION AND FLAME. 



269 



indeed, it is probable that no degree of heat whatever would 
make common air or any other gas visible. We may heat 
a combustible gas, like the olefiant, to a point when it will 
take fire in the air. This we do, in fact, when we touch it with 
the flame of a candle. The current of heated air ascending 
from an argand lamp chimney is invisible ; but a thin wire 
held in it will at once glow with bright redness, showing that 
the air is highly heated. A few bodies, when intensely 
heated in the air, suffer no change ; such are gold, platinum, 
palladium, and other metals not easily oxydized. The term 
incandescence expresses the condition of such bodies, and 
varies in intensity with the degree of heat. A while heat is 
considered equal to about 3000°. A much lower temperature 
will inflame most combustible bodies, and the combustion, 
when once begun, is continued without further addition of 
outward heat, as is seen in our common fires. The at- 
mosphere in such cases supplies all that is required to con- 
tinue the combustion. 

464. The structure of fiame deserves our particular 
attention. Flame is ignited, combustible, aerial matter. 
All these conditions are needed to constitute flame, as a 
moment's attention will show. The 
flame can burn only in contact 
with the air, and must therefore 
consist of an exterior ring or 
shell of flame, and an interior 
cone of uninflamed combustible 
matter. A common candle or 
lamp shows those conditions per- 
fectly. The wick draws up the 
tallow or oil, which is converted 
into a volatile hydrocarbon, as 
soon as it touches the ignited 
portion of the wick, or hot atmosphere 
of flame. This combustible can burn only in contact with 
oxygen ; and that the interior portion (a) is actually inflam- 
mable gas, is very easily proved, since it can be led out by 
a small glass tube, (&,) and set fire to from its other end. 




How is the high temperature of heated air made evident ? How 
high is the temperature of whiteness ? 464. What is flame ? How 
does flame burn? Illustrate this in the case of the common candle. 
How is the interior portion seen to be combustible ? 

23* 



270 



NON-METALLIC ELEMENTS. 



In like manner, by bringing a sheet of platinum foil over the 
flame of a large spirit-lamp, it will be heated to redness in a 
ring, while the centre will remain black, showing that the 
interior is comparatively cold, and the exterior intensely 
hot. Phosphorus may be placed on the expanded wick of 
a large alcohol-lamp, or on a tuft of cotton wet with alcohol, 
and after kindling, it can be at once extinguished, by setting 
fire to the alcohol, which, rising in a voluminous flame, 
envelops the phosphorus in an atmosphere that cannot 
sustain its combustion, and consequently it ceases to burn, 
but commences again as soon as the air comes in contact 
with it. 

465. The temperature of flame is much higher than that 
of ignited solids, even when the color of the flame is very 
feeble, as of alcohol or pure hydrogen. The quantity of 
light which flames emit is dependent on the presence of 
minute particles of solid matter, which glow with the intense 
heat, and reflect a strong light. This result is experienced 
when the flame of the oxyhydrogen blowpipe falls on lime 
or platina ; and the brilliant focus of the galvanic light is 
probably filled with the vapor of volatilized carbon, or of the 
metals suffering combustion. The carbohydrogen gases 
burn with such intense brilliancy, on account of the minute 
particles of carbon derived from the decomposition of the gas 
by the heat, which burn in the air, and thus give the strong 
light peculiar to these compounds. When the particles of 
free carbon become too numerous, 
and there is not oxygen enough to 
burn them, the flame smokes. A 
common tallow candle is in this con- 
dition, and is therefore a very im- 
perfect means of illumination. The 
various contrivances in common use, 
as argand and solar lamps, &c, have 
for their object to raise the temperature 
of the flame so high, by a full supply 
of oxygen, as to leave no carbon 




Illustrate this by phosphorus. 465. What is said of the tempera- 
ture of flame ? On what does the luminousness of flame depend >. 
Illustrate this. "When the free carbon becomes too abundant, what 
happens ? How do the argand and solar burners improve the 
quality of flame 



COMBUSTION AND FLAME. 271 

unburnt. The quantity oflight thus obtained from the same 
quantity of oil is greatly increased, ana 1 all inconveniences 
from smoke and bad odors avoided. 

The common laboratory lamp illustrates this principle, as 
seen in the sectional figure. It will be observed that there is 
a central opening vertically through the lamp, which allows 
a column of air to draw up within the circular wick, and the 
flame is thus doubled, as compared with the common spirit- 
lamp, or candle. 

466. The student who resides where gas is used for 
illumination, possesses a ready means of 
procuring a very powerful and economical 
heat, which he can command at pleasure, 
by regulating its intensity with a stop-cock. 
It is always ready and can be 
left for any length of time. 
With a mica chimney and a 
moveable foot connected with a 
flexible gas-pipe, the gas-lamp 
may be placed where the con- 
venience of the operator re- 
quires. A small glass spirit-lamp with a close cover to pre- 
vent evaporation, is an indispensable convenience even in the 
humblest laboratory. 

467. Dr. C. T. Jackson has contrived a modification of 
the common argand spirit-lamp, which is the most powerful 
lamp-furnace in use. This invention consists in applying 
the principle of the mouth-blowpipe to the argand-lamp, and 
is accomplished by forcing a blast of air or of pure oxygen 
gas from a bellows, into the bottom of a tube within that 
which carries the circular wick. The arrangement is such, 
that the blast issues in a narrow ring concentric with the 
wick and in close contact with it. The wick is turned up 
pretty high, and the lower orifice of the argand tube stopped 
with a cork, when the blast is in use. By this lamp 600 
grains of carbonate of soda are readily fused in a platinum 
crucible, and many operations accomplished which usually 
require a furnace heat. The supply of air or gas is regula- 
ted by a screw on the bottom of the blast tube, and the bel- 
lows to supply the blast is placed beneath the table and worked 



What is the principle of this structure ? 466. What is the gas- 
iamp ? 467. Describe Dr. Jackson's lamp. «* 





— u- 



272 



NON-METALLIC ELEMENTS. 





convert the 



» 



by the foot. If the intense heat is not wanted, the lower 
orifice is opened, and the lamp then becomes only a power- 
ful argand. The chimney of this lamp must be made of 
mica, to withstand the heat. 

468. The mouth-blowpipe enables us 
flame of a com- 
mon candle or 
lamp into a pow- 
erful furnace. By 
the blast from the 
jet of the blow- 
pipe, the operator 
turns the flame in 
a horizontal direction upon the object of 
experiment, at the same time that he sup- 
plies to the interior cone of combustible 
matter a further quantity of oxygen. The 
flame suffers a remarkable change of 
appearance as soon as the blast strikes it, 
and the inner blue point has very different 
chemical effects from the exterior or yellow 
point. Immediately before the exterior 
flame is a stream of intensely heated air, 
which is capable of powerfully oxydizing a 
body held in it, and this point is therefore 
called the oxydizing flame. The inner or 
blue point is called the reducing flame, and in it all metallic 
oxyds capable of reduction are easily reduced to the metallic 
state. or a lower degree of oxydation. Between the outer 
and inner flames is a point of most intense heat, where 
refractory bodies are easily melted. Charcoal is generally 
employed to support bodies before the blowpipe flame, when 
we would heat them in contact with carbon. Forceps of pla- 
tinum are used to hold the substance when it is to be heated 
alone ; and a small wire of the same metal, with a little 
loop bent on one end, is used to hold a globule of fused car- 
bonate of soda, or other flux, when we wish to submit a body 
to the action of such rcageants. The art of blowing an un- 
intermitting stream is soon acquired, by breathing at the same 



i 



468. What does the mouth-blowpipe accomplish ? Describe the 
flame. How does the blast affect it ? Distinguish between the 
reducing and the oxydizing flames. 



COMBUSTION AND FLAME. 273 

time through the mouth and nostrils ; and an experienced 
operator will blow a long time without fatigue. No instrument 
is more useful to the chemist and mineralogist than the 
mouth-blowpipe. By its means we may in a few moments 
submit a body to all the changes of heat, or the action of rea- 
geants, which can be accomplished with a powerful furnace.* 
469. The temperature of fame may be so reduced by 
bringing cold metallic bodies'near it as 
to be extinguished. On this simple 
fact rests the power of the " safety 
lamp" of Sir Humphrey Davy to protect the life of the miner. 
If a narrow coil of copper wire be brought over a candle or 
lamp so as to encircle it, the flame will be extinguished ; but 
if the wire be heated previously to redness, the flame con- 
tinues to burn. The same effect will be produced by a small 
metallic tube. A wire held in the flame is seen to be sur- 
rounded with a ring of non-luminous matter. If many wires, 
in the form of a gauze, are brought near the flame of a can- 
dle, it will be cut off and extinguished above ; only a current 
of heated air and smoke will be seen ascending, while the 
flame continues to burn beneath and heats the wire «;auze red- 
hot in a ring, marking the limits of the flamo. The flame 
may be relighted above the gauze, and will then burn as 
usual, as seen in the second figure. Sir Humphrey Davy 
found that a wire gauze would in all cases arrest the progress 
of flame, and that a mix- // . 

ture of explosive gases fly 

could not be fired through 
it. A wire gauze is only 
a series of very short 
square tubes, and their 
power to arrest flame 
comes from the fact that 



469. How do cold metallic bodies affect flame ? What valuable 
instrument is based on this fact ? How does wire gauze affect flames ? 
What may the wire gauze be considered ? What temperature do the 
carbohydrogens require for their combustion ? 



* The student would do well to consult " Berzelius on the Blow- 
pipe," translated by J. D. Whitney. Boston, 1845 ; Ticknor & Co. ; 
12mo. pp. 237. 




274. 



NON-METALLIC ELEMENTS. 



they cool the gases below their point of ignition. Providen- 
tially, the heat required to ignite the carbon gases is much 
higher than that which will produce the union of oxygen and 
hydrogen. 

470. Safety Lamp. — The explosion of inflammable gases 
in coal mines has destroyed thousands of those whose duties 

required them to submit to the exposure. To 
avoid these lamentable accidents, Davy invented 
the miner's lamp, which is only a common lamp 
surrounded by a cage of wire gauze completely 
enclosing the flame. When this lamp is placed 
in an explosive atmosphere, the gas enters the 
cage, enlarges the flame on the wick, and burns 
quietly, the gauze effectually preventing the pas- 
sage of the flame outwards. We thus enter the 
camp of the enemy, disarm him, and make him 
labor for us. The miner is not only protected 
by this instrument, but is rendered conscious of 
his danger, by the enlargement of his flame. 
As long as the lamp can burn, it is safe to stay, 
as an irrespirable atmosphere would extinguish 
the flame. The powerful blast of wind which 
sometimes sweeps through the mines may render 
the lamp unsafe, by forcing the flame against the gauze, 
until it is heated so hot as to inflame the external atmosphere. 
This accident is prevented by the addition of a glass to cover 
the sides, the air being admitted from below through flat 
gauze discs. 

471. The phenomena of the safety lamp may be easily 
illustrated by the teacher, with a large bell glass placed over 
a naked lamp and left open beneath. Hydrogen may be 
admitted from below by a gas-pipe, when the atmosphere soon 
becomes explosive and goes off, extinguishing the lamp. 
The miner's lamp under the same circumstances, will first 
burn with an enlarged flame, and then go out quietly, as soon 
as the air can no longer support the combustion. 



470. For what use was the miner's lamp contrived ? How is it 
constructed ? How does it indicate the state of the atmosphere in 
the mine? 471. How are the phenomena of the safety lamp illus- 
trated ? 



METALLIC ELEMENTS. 275 

II. METALLIC ELEMENTS. 

1. General Properties of Metals. / ffCt 

4H2. The number of the metallic elements is about forty-two, 
or three times the number of the non-metallic bodies, which 
have already engaged our attention. If we include five lately 
proposed new metals, we shall have forty-seven bodies in this 
class. Of all this number, however, a few only are of con- 
siderable interest, while many (at least half) are totally un- 
known in common life. The minerals which contain several 
of the rare metals, in combination with various substances, 
are among the most uncommon specimens of mineralogical 
cabinets. 

473. A metal is a body which conducts electricity and 
heat, which is opaque, and has a peculiar brilliancy, known 
as the metallic lustre. It has been before remarked (251) 
that metallic lustre is the only property which belongs pecu- 
liarly and solely to this class of bodies. A metal, when 
submitted in solution to electrolysis, is always given out 
at the negative side of the battery, and is therefore a positive 
electric. Any body which possesses these general properties 
is a metal, according to our present notions of the metallic 
character. We see every variety in some of these charac- 
ters. Some metals are almost without lustre, as manganese, 
while others, like gold and silver, may stand as examples 
of perfection in this as well as in all other metallic properties. 
Opacity is not complete even in gold and mercury, as already 
mentioned, (53.) Some metals are perfectly malleable when 
cold, as silver, gold, lead, and tin ; others are malleable when 
hot, as iron, platinum, &c, and are not without this property, 
though in a less degree, even when cold. Some, like zinc, 
are laminable at a moderate heat, but brittle above and below 
it ; others, like antimony, are brittle at all temperatures short 
of fusion. We have already explained (18) the properties 
of brittleness, malleability, ductility, and laminability. The 
tenacity of metals depends much- on their relations to these 

472. What is the number of metallic elements ? How many of 
these are of much importance ? 473. What is a metal ? How do 
they act in electrolysis ? What variety is seen in the metallic 
character ? Is opacity perfect in them ? Mention their characters. 



276 METALLIC ELEMENTS. 

properties. Iron is an example of great tenacity and duc- 
tility, while in malleability it is much inferior to gold and 
silver. 

474. The tenacity of metals is compared by using wires 
of the same size of different metals, and ascertaining how 
much weight they will sustain. Iron is the most tenacious, 

and lead the least. Wires are drawn through 
[~\ smooth conical holes in a steel plate, each 
succeeding hole being a little less than its pre- 
decessor. In this way wires of extreme fine- 
ness may be drawn from several of the ductile 
metals. Dr. Wollaston succeeded, by a pecu- 
, . / liar method, in making a gold wire so small 
*-* that 530 feet of it weighed only one grain ; it 
was only 50 1 00 of an inch in diameter ; and a platinum wire 
was made by the same philosopher, of not more than -g ^oo 
of an inch. Metals passed repeatedly through the rolling- 
mill, or wire plate, become stiff and brittle, but are again 
made soft by heating them to redness and cooling them 
slowly. This is called annealing. Copper is annealed by 
plunging the red-hot metal into cold water, while the same 
treatment renders iron and steel extremely hard. 

475. The fusibility and density of metals differ very 
much. Platinum is at once the most dense of all bodies, 
being 21 to 21*5, and also one of the most infusible. Gold 
is next in density, (19-26,) but fuses at 2016° F. Palladium, 
uranium, cobalt, nickel, iron, molybdenum, manganese, 
columbium, tungsten, and titanium, are all infusible below 
3000°, (the heat of the most powerful air furnace; and 
most of these are altogether infusible. In density, sodium 
and potassium occupy the lowest points, (-972 and -865,) 
being less in density than water, and they also fuse at the 
low temperature of 190° and 136.° 

476. Metals vary also in volatility as much as in other 
properties. Mercury boils at 662°, and arsenic, tellurium, 
cadmium, zinc, potassium, and sodium, are also volatile at 



474. How is the tenacity of metals compared ? Explain the use 
of the wire plate. How fine have wires of gold and platinum been 
made ? What is annealing ? How is it accomplished in different 
metals ? 475. How do the density and fusibility of metals com- 
pare ? 476. How do metals compare in volatility by heat ? 
Mention some of the volatile ones. 



GENERAL PROPERTIES OF METALS. 277 

temperatures below a red heat. It is not ^impossible that all 
the metals would be volatile, if we could heat them highly- 
enough ; but many of them, as gold, platinum, silver, &c, 
may be exposed to the highest heat of a wind-furnace with- 
out change. Some metals assume a semi-fluid or pasty con- 
dition before melting, such as platinum and iron, both of 
which can be welded or made to unite without solder, when 
in this soft state ; lead, potassium, and sodium, can be 
welded in the cold, as also can mercury, when it is frozen. 
In cooling from fusion, some metals crystallize beautifully, 
of which bismuth is an example, while others, as gold and 
platina, are not commonly seen in the crystalline form. 

477. The metals are rarely found in their metallic state 
in nature. Their characters are generally masked under 
some form of combination with oxygen or sulphur. Thus, 
iron is perhaps never seen in a malleable form in mines. 
The masses of malleable iron found on the surface of the 
earth are probably all of meteoric origin, having fallen 
through the atmosphere to the earth. Some metals, as gold, 
silver, platinum, copper, bismuth, and a few others, are 
frequently found native, or in the malleable form, either pure 
or alloyed with each other. An alloy is the union of two 
metals, as of copper and zinc, to form brass, and lead and 
tin, to make pewter, &c. Gold is usually found alloyed 
with silver, and platinum has generally several rare metals 
alloyed with it. Alloys are feeble chemical combinations; 
and are usually best suited to artificial purposes when made 
in the atomic proportions of the several metals. The alloys 
of mercury are called amalgams. Copper and tin unite in 
several distinct proportions, forming very unlike alloys, as 
gun and bell-metal, and speculum-metal. Several distinct 
compounds of gold with silver, and also of other metals, 
have been recognised. 

478. In their chemical relations the metals are highly 
electro-positive, and form compounds with all the members of 
the oxygen group, and with phosphorus, carbon, &c. They 



What is said of the possible volatility of others ? On what pro- 
perty does welding depend ? What of the crystallization of metals ? 
477. In what state do the metals occur in nature ? With what are 
they generally combined ? Which are frequently in a metallic 
state ? What are alloys ? Are they in atomic proportions ? What 
are the alloys of mercury called ? 478. In their chemical relations 
the metals are what ? 
24. 



278 METALLIC ELEMENTS. 

all unite with oxygen, and usually in more than one propor- 
tion, but their affinity for this element is very various. The 
majority of metals will combine slowly with the oxygen of 
the air, forming a coating of oxyd, (or rust,) which usually 
protects the metal from further action. This is the case 
with lead, zinc, copper, and iron. Sodium and potassium, 
and the metals of the alkalies generally, have so strong an 
affinity for oxygen as to be able even to decompose water at 
all temperatures. 

479. The oxyds of the metals may be divided into three 
classes. 1st, the protoxyds, which are strongly basic ; 2d, 
neutral, or those which are neither basic nor acid ; 3d, those 
which are decidedly acid in their relations. The changes 
of character in oxyds, have a uniform relation to the amount 
of oxygen they contain, the higher oxyds being either neutral 
or decidedly acid. Thus the protoxyd of manganese is a 
strong base, the deutoxyd is feebly basic, the peroxyd is 
indifferent, and the higher oxyds are the manganic and per- 
manganic acids ; which are capable of replacing sulphuric 
and hyperchloric acids. Arsenic and antimony have no 
protoxyds, and are remarkable for forming strong acids with 
oxygen, (250, Class IV.) By this feature they are closely 
assimilated, as has already been remarked, to the non-metallic 
bodies. 

480. The compounds which the metals form with chlorine, 
iodine, sulphur, &c, bear a very striking analogy in compo- 
sition to the oxyds of the same metals. So true is this, that 
knowing what oxyds a given metal forms, we can almost 
certainly tell what the composition of its sulphurets, chlorids, 
&c, will be. Thus the oxyds of iron being FeO and Fe0 2 3 , 
we find that the sulphurets of the same metal are FeS and Fe 2 S 3 , 
and the chlorids FeCl and Fe 2 Cl 3 . It might be inferred from 
this statement, that where these metallic bodies unite with 
acids to form salts, there would be the same conformity 
among them that is found among their bases, and such we 
shall find to be the fact. 



What is their affinity for oxygen ? 479. How are the oxyds 
divided ? What characters have these three classess ? On what 
does this character depend ? Illustrate this in the case of manga- 
nese. What metals are remarkable for forming acids ? To what 
are they thus assimilated ? 480. To what are the metallic chlorids 
analogous? Illustrate this. What inferences regarding the saline 
compounds of those bodies ? 



GENERAL PROPERTIES OF METALS. 279 

481. Combinations of the metallic oxyds, chlorids, sul- 
phurets, &c., take place always among members of the same 
series, that is, oxyds with oxyds, chlorids with chlorids, sul- 
phurets with sulphurets, and so on : those members of the 
same series which differ greatly in character being most 
disposed to unite, as the oxygen acids with the oxygen 
bases, &c. Thus, sulphuric acid (a powerful oxygen acid) 
and protoxyd of iron (a powerful oxygen base) unite to form 
a salt which is entirely neutral, and in which the properties 
of neither constituent are sensible, having the formula 
FeO, S0 3 for the dry sulphate of iron. 

482. Compounds which belong to unlike or different 
series, on the contrary do not unite, but often mutually de- 
compose each other. Thus, when hydrochloric acid and 
potash are brought together, both are decomposed, water and 
chlorid of potassium being formed, as may be understood 
from the following symbols : 

Potash. Hydrochloric acid. Water. Chlorid of Potassium. 
KO + HC1 _= HO + KG1 

The latter remains in solution, and may be obtained in 
crystals on evaporation. 

483. When any base unites with an acid to form a neu- 
tral salt, there must be as many equivalents of acid em- 
ployed, as there are of oxygen in the base itself. The same 
is true also of those acids which contain no oxygen, as the 
hydrochloric, provided the metallic oxyd dissolves in hydro- 
chloric acid without the evolution of chlorine. For example, 
peroxyd of iron dissolved in hydrochloric acid produces 
water and a perchlorid of iron : 3HC1 and Fe 2 3 giving rise 
to 3HO and Fe 2 Cl 3 . 

484. Theory of Salts. — The binary compounds of chlo- 
rine, iodine, &c, with many of the metals, particularly those 
of the alkaline class, have in an eminent degree the properties 
of salts, and among them we recognise particularly the 



481. How do combinations among metallic oxyds, &c, take 
place ? Illustrate this by sulphuric acid and protoxyd of iron. 482. 
Compounds which belong to different series act how ? Illustrate 
this by potash and hydrochloric acid. 483. What condition of neu- 
trality is here stated in the formation of salts ? How in case of 
hydrochloric acid ? Illustrate this in case of peroxyd of iron and 
HC1. 484. What are the binary compounds of the oxygen group 
like ? 



280 METALLIC ELEMENTS. 

chlorid of sodium or common salt, which is the parent, it 
may be said, of all salts, or that body from which they are 
all named. If the old definition of a salt, however, be ad- 
mitted, those bodies cannot be called salts, since according 
to that view a salt is a compound of the oxyd of a metal with 
an oxygen acid. To avoid this difficulty, two classes of 
salts have been instituted, the first of which includes all 
those binary compounds which, like common salt, have a 
metallic base in direct union with a salt-radical ; and the 
second includes those salts which, like sulphate of soda, are 
supposed to be constituted of the oxyd of the metal and an 
oxygen acid. The first have been called the haloid* salts, 
and the second the oxy-salts. 

485. The term " salt-radical" just employed, includes 
not only all the members of the oxygen group, except oxy- 
gen itself, but also all those compound bodies which, like 
cyanogen, and numerous similar substances, act the part of 
elements in the formation of compounds. 

In stating the constitution of sulphuric acid, (294,) it will 
be remembered that the expression S0 4 + H was employed as 
an equivalent to S0 3 + HO. It is claimed that all the hydra- 
ted acids are in reality compounds of hydrogen with a simi- 
lar radical, and accordingly nitric acid will be N0 6 -fH, 
instead of N0 5 + HO. One principal objection to this view 
is, that these hypothetical radicals have never been isolated. 
But the same is true of N0 5 , which is entirely an unknown 
body, and so are nearly all the organic acids, independently 
of water or hydrogen. Moreover, those acids which are capa- 
ble of existing dry and in a separate state, as sulphuric, (S0 3 ,) 
phosphoric, (P0 5 ,) and carbonic, (C0 25 ) are not acids as long 
as they remain dry, and although they form compounds with 
dry ammonia, these compounds are not salts. Sir Hum- 
phrey Davy long ago proposed to consider hydrogen as the 
real acidifying principle in all acids. This view of the case 
is therefore by no means new. What we now know of the 



What is the definition of a salt ? What two classes of salts have 
been instituted to meet this difficulty ? 485. What bodies are in- 
cluded under the term salt-radical ? What is the salt-radical view 
of the composition of sulphuric acid? State the objections against, 
and reasons for this view. 



From hals t sea-salt, and eidos, in the likeness of. 



GENERAL PROPERTIES OF METALS. 281 

metallic character of hydrogen, goes to confirm his theory. 
If the salt-radical theory is to be adoptecT, all acids will be 
considered as hydrogen acids, and all salts as haloid salts. 
For example, let us take two common saline bodies and pre- 
sent them according to these two views.* 

Old view. New view. 

Sulphate of zinc, ZnO + S0 3 Zn + S0 4 

Nitrate of soda, NaO -+- N0 5 Na •+• N0 6 

486. According to the new view, when an acid dissolves 
a metal, there is no necessity for supposing water to be de- 
composed. The metal takes the place of the hydrogen, and 
the latter is given off in a gaseous form ; or if the oxyd of 
the metal is used, the oxygen and hydrogen unite to form water, 
and no effervescence ensues. We shall consider the saline 
compounds of the metals under each, and not devote a sepa- 
rate part of the work to their discussion. The nomenclature 
of the salts has already been explained, (201,) and need not 
be repeated here. 

2. Classification of Metals. 

487. Until we are more familiar than we now are, with 
all the principles of isomorphism, with the constitution of 
many metallic oxyds, sulphurets, &c, and the relations 
which the study of organic chemistry is constantly unfold- 
ing, it will not be found easy to name an unexceptionable class- 
ification for the metallic bodies. The order in which the 
metals are discussed in the following pages, does not differ 
materially from that generally followed in elementary works, 
and it is presumed that it will be found well adapted to the 
purposes of the general student. 



Give the constitution of sulphate of zinc and nitrate of soda on 
the old and new views. 486. How according to the new view, do 
metals and oxyds dissolve in acids ? 487. What is said of the 
classification of the metals ? What classification is followed here ? 



* It is impossible to do justice + o the new theory of salts in so 
limited a space as we allot ourselves, and the reader who wishes to 
seek further information, is referred to Mr. Graham's Elements of 
Chemistry, p. 158, English edition This view has been strongly- 
controverted, and is frequently rejected. In this country it has been 
ably contested by Dr. Hare. See Am. Jour. Scie?ice, vol. i. 2d 
series, p. 82. 377. 
24* 



282 



METALLIC ELEMENTS. 



CLASS I. METALS OF THE ALKALIES. 

15. POTASSIUM. 

Equivalent, 39*19. Symbol, K. (Kalium.) Density, *865. 

488. History. — Potassium was discovered by Sir Hum- 
phrey Davy in 1807; at the same time with its congeners, 
sodium, barium, strontium, and calcium. Before that time 
the alkalies and alkaline earths were looked upon as simple 
elementary bodies, and were so treated in all chemical works. 
Davy found that on passing the electric current from a pow- 
erful voltaic battery, through a cake of moistened potash, 
both electrodes being of platinum, violent action followed, 
oxygen was evolved with effervescence at the positive pole, 
and bright metallic globules, like mercury, accompanied by 
hydrogen gas, appeared at the negative pole. Some of these 
globules flashed and burnt with a violent light as they reached 
the air, and others remained and were soon covered with a 
white film that formed on their surfaces. These globules 
were the metal potassium, and its discovery constitutes one 
of the most interesting chapters in chemical history. 

Potassium in combination, chiefly as silicate of potash, is 
widely diffused over the globe. It forms a part of all fertile 
soils, and the chief source from which it is artificially pro- 
cured is the ashes of hard-wooded forest-trees, which derive 
it from the soil on which they grow. It is also present in 
sea-water, as chlorid of potassium, and is found in the ashes 
of sea-plants. 

489. Preparation. — The expensive and troublesome 
method of procuring this metal by galvanism has been 
replaced by a much more convenient and productive furnace 
operation, founded on the decomposition of potash at a white 
heat by charcoal. For this purpose carbonate of potash is 
intimately mixed with charcoal, which is best prepared by 
igniting cream of tartar in a covered crucible, which yields a 
black mass commonly known as black flux, consisting of 
carbonate of potassa, and charcoal derived from the organic 
acid. This mass is finely powdered, and one-tenth part of 



488. "What is the symbol and equivalent of potassium ? When, 
and by whom, and how was it discovered ? How is this metal 
found in nature ? 489. How is potassium prepared ? 



POTASSIUM. 283 

charcoal in small lumps being added to it, the whole is trans- 
ferred to an iron retort, formed of a quicksilver bottle, and 
laid horizontally in a powerful wind furnace. A short iron 
tube connects the iron bottle with a copper vessel of peculiar 
construction, containing naphtha, and kept cold. The bottle is 
then gradually raised to an intense heat, having been pre- 
viously protected by a well-dried coating of sand-luting to 
guard the iron against fusion. Decomposition of the carbon- 
ate of potash follows, carbonic oxyd gas escapes, and metal- 
lic potassium distils over in melted globules, which fall into 
the naphtha, where they are preserved. Many precautions 
are required to insure success, and particularly to see that 
the tube of delivery does not become stopped ; to guard 
against which, the apparatus is so constructed that a strong 
iron rod can be thrust in to clear the opening. 

The first product is not pure, and must be redistilled in a 
small iron retort, with a little naphtha, into a receiver con- 
taining that liquid. It is requisite to employ naphtha in this 
process, because it contains no oxygen in its constitution, and 
does not readily suffer change from the action of potassium. 

490. Properties. — Potassium, when recently obtained, is 
a brilliant, silver white metal, possessing the metallic lustre 
in an eminent degree. At common temperatures it is soft 
like putty, and may be easily moulded or welded by the 
fingers. It is the lightest metal known, having a density of 
only -865 ; consequently it floats on water, for the oxygen of 
which it has so great an affinity as to decompose it at all 
temperatures. It burns brilliantly on the surface of the 
water with a beautiful violet purple flame, and is rapidly 
propelled over its surface by the gases and vapors evolved 
in the combustion, forming one of the most attractive of chem- 
ical experiments. The hydrogen of the decomposed water 
also burns at the same time. Any considerable quantity 
thrown on water will explode violently, scattering the burning 
metal in all directions. Exposed to the dry air, it soon 
tarnishes, and gradually falls to a white powder, (potash.) 
Its metallic lustre may be beautifully seen by melting it 
under naphtha, when it is extremely brilliant. At 30° it is 
brittle and crystallizes in cubes ; at 150° it melts, and below 



Describe the arrangement. How is the metal preserved ? 490. 
Give its density. What is its strongest affinity ? What is its action 
on water ? How does air affect it ? How does heat affect it I 



284< METALLIC ELEMENTS. 

redness it boils and is raised in vapor. It may be distilled 
unchanged, in vessels free from oxygen. 

491. The uses of potassium are purely scientific. It is a 
most powerful means of research, since its affinity for oxy- 
gen is so great as to enable it to decompose the chlorids of 
aluminium, glucinum, yttrium, thorium, magnesium, and zir- 
conium, yielding to us the metallic bases of these compounds. 
It is also, as will be remembered, (356 and 368,) the means 
by which silicon and boron are obtained. 

1. Compounds of Potassium. 

492. Potassium combines with all the members of the 
first three classes, forming bodies several of which are of 
great importance in the arts and in pharmacy. We can de- 
scribe only a few of the most important of these compounds. 

493. The Oxyd of Potassium is formed only when 
potassium is exposed to dry oxygen or common air. It is a 
white powder, strongly alkaline, which has a great affinity 
for water, forming with it three distinct hydrates, the first of 
which is caustic potash, (KO,HO.) This hydrate is a 
white solid, which fuses at a temperature near to redness ; 
but no degree of heat will expel the equivalent of water with 
which it is combined. On cooling, it forms a somewhat 
crystalline, compact mass, which has a great avidity for 
water, attracting it rapidly from the atmosphere. Half its 
weight of water will dissolve it, and it is also soluble in 
alcohol? It is best prepared by decomposing pure carbonate 
of potash, dissolved in 10 parts of water in a clean iron 
vessel, with half its weight of good quick-lime, previously 
slaked and mingled with so much water as to form a thin 
paste, called milk of lime. This is added in small portions 
to the potash solution while the latter is boiling, a short 
interval being allowed between each addition ; all the lime 
being added, the whole is boiled for a few minutes, and then 
is removed from the fire and covered up. Care is needed to 
keep the solution dilute, to prevent the caustic potash formed 
from decomposing the resulting carbonate of lime. After 



491. What are its uses? .What other bodies have been produced 
by its means ? 492. Name the compounds of potassium with the 
oxygen group. 493. How is its oxyd formed ? What is its hydrated 
oxyd called ? What are the properties of the hydrate of potash ? 
How is it prepared ? 



COMPOUNDS OF POTASSIUM. 285 

standing a few hours, until all the lime Jjas settled and the 
liquid is clear, it is drawn off by a syphon, and concentrated 
by boiling in a clean iron pan or silver capsule, until it has 
an oily consistence, when it is poured out upon a clean 
surface of iron or marble; it then hardens into the white 
solid hydrate called caustic potash. To insure its purity, it 
may be dissolved in absolute alcohol, which will leave 
behind its impurities. The alcohol is expelled from the 
decanted solution by heat, and the solid potash recovered by 
fusion in a silver crucible. The moderately strong solution 
of potash answers most of the purposes of the laboratory as 
well as the solid hydrate. 

494. The solution of caustic potash is intensely alkaline, 
saturates the most powerful acids, restores the colors of 
reddened vegetable blues, and turns many of them green ; 
it has an acrid and most disgusting taste, peculiar to alkalies, 
and, when strong, attacks all organic matters, dissolving and 
disorganizing them. Its solution feels soapy on the ringers, 
and forms compounds with fats, called soaps. The solid 
potash is often used as a caustic by surgeons, whence its 
name. Silica is dissolved by it. Its solution absorbs car- 
bonic acid perfectly, and is employed for that purpose in 
organic analysis ; the solid potash removes both carbonic 
acid and moisture from the air, and is therefore sometimes 
used in desiccation. 

495. The presence of potash in solution may be de- 
tected by an alcoholic solution of the chlorid of platinum, 
which throws down a yellow crystalline precipitate in a 
concentrated solution. Perchloric, tartaric, and hvdrofluo- 
silicic acids, are also tests of the presence of potash, which 
forms with all of them precipitates but little soluble in water. 

496. Peroxyd of Potassium is an orange-yellow powder, 
formed by passing oxygen over potash heated to redness in 
a tube. It is decomposed by water, oxygen being given off, 
and a solution of potash remaining. 

497. Chlorid of Potassium may be formed by the direct 
combustion of potassium in chlorine gas, which takes place 

To insure its entire purity, how is it treated ? 494. What are 
the properties of its solution ? What compounds does it form with 
fats ? Why is it called caustic ? Name some of its other uses and 
properties. 495. How is its presence detected ? 496. Peroxyd of 
potassium is how prepared ? 497. How is' the chlorid made, and 
what are its properties ? 



286 METALLIC ELEMENTS. 

spontaneously. It is also formed by dissolving potash in 
dilute hydrochloric acid to saturation, when cubic crystals of 
chlorid of potassium are obtained on evaporating the solution. 
It is also left as a residuum after the oxygen process, (253.) 
It has a bitter saline taste, and does not preserve meats, like 
the chlorid of sodium. 

498. Bromid of Potassium is prepared by saturating a 
solution of potash with bromine, evaporating the solution and 
igniting the residuum in a covered crucible of platinum or 
iron. The melted mass is bromid of potassium, and may 
be turned out to cool on an iron plate. In the solution, both 
bromate of potash and bromid of potassium exist, but the 
ignition expels oxygen, and only the bromid is left. It is a 
white soluble salt, which crystallizes in cubes, and is soluble 
in alcohol. The crystals are anhydrous, and decrepitate 
when heated, like common salt. Bromid of potassium is 
frequently found in the waters of saline springs and inland 
seas. 

499. Iodid of Potassium, formerly called kydriodate of 
potash, is a compound of great use in medicine, being the 
form in which iodine is usually employed in medical prac- 
tice. It is obtained by a process similar to that just 
described for the bromid, and also by decomposing the iodid 
of iron, by a solution of potash. It is a white salt in cubic 
crystals, very soluble in both alcohol and water. Its solution 
dissolves a large quantity of free iodine, acquiring thus a 
deep brown color. 

500. Fluorid of Potassium is obtained by the action of 
hydrofluoric acid on potash. It is perfectly analogous to the 
preceding salts, crystallizes in cubes, and is very soluble in 
water. 

501. Sulphuret of Potassium. — Sulphur combines with 
potassium in several proportions — probably in seven. The 
protosulphuret of potassium is made by melting together its 
constituents, or better by passing hydrogen gas over the 
neutral sulphate of potash heated to redness. Water is 
formed, and sulphuret of potassium remains. It is a bright 
red solid, and forms a colorless solution in water, which has 

498. Describe the formation of bromid of potassium. 499. What 
use is made of iodid of potassium ? What are its properties ? 500. 
Fluorid of potassium is how prepared ? What crystalline form is 
common to all the foregoing salts ? 501. What are the compounds 
of sulphur and potassium ? Describe the sulphurets. 



COMPOUNDS OF POTASSIUM. 2^7 

an alkaline reaction. This is a sulphur bas^of considerable 
power, and combines with sulphur acids without decompo- 
sition. Other acids decompose it with the escape of sulphu- 
reted hydrogen. The tritosulphuret of potassium (KS 3 ) 
corresponds to the teroxyd of the same base. 

502. The Pentasulphuret of Potassium (per sulphur et KS 5 ) 
is formed when sulphur is fused with carbonate of potash at as 
low a heat as possible ; hyposulphite of potash is formed at 
the same time. The persulphuret is a deep orange-yellow 
solid, soluble in alcohol. 

The protosulphuret is converted into the persulphuret by 
boiling in water with four equivalents of sulphur. 

The Seleniurets of Potassium are supposed to be like the 
sulphurets, but are not much known. 

503. Nitrogen forms a compound with potassium, (K 3 N.) 
When potassium is heated in dry ammonia, an olive-green 
solid is formed, which has the composition expressed by 
K,NH 2 . When this is heated, ammonia escapes, and a 
gray body resembling graphite is left 'behind, which is the 
compound in question. Phosphorus also forms a solid com- 
pound with potassium — the phosphuret of potassium — which 
is decomposed by water with the escape of spontaneously 
inflammable phosphureted hydrogen. 

Unimportant compounds are also formed by potassium 
with carbon and hydrogen ; but no compound is known be- 
tween it and silicon and boron. 

2. Salts of Potash. 

504. The salts of potash are numerous and important. 
We shall however mention now only the carbonates, sul- 
phates, nitrate, and chlorate. As it will be altogether im- 
possible to give even the names of all the salts of the metals, 
we must content ourselves with a selection of the most 
important and interesting. 

505. Carbonate of Potash, KO,C0 2 +HO, (79-19.)— 
This salt, in an impure form, is made on a great scale in 



502. The pentasulphuret is what, and how formed ? 503. What 
is the compound of nitrogen and potassium, and how formed ? What 
other compounds of potassium with non-metallic element? are 
named ? 504. What is said of the salts of potash, and which} will 
be now considered ? 505. What is the formula and atomic number 
of the carbonate of potash ? 



288 METALLIC ELEMENTS. 

this country, under the name of pearlash and potash, which 
is the alkali obtained from the ashes of forest trees, by lixi- 
viation and combustion. 

The crude article of commerce is contaminated by silica, 
suiphate of potash, and chlorids of potassium and sodium. 
The latter impurity is frequently added in the process of 
manufacture, either through ignorance, or from fraudulent 
motives. The best potash is made by using hot water to 
lixiviate the ashes, in small leach-tubs. The brown mass 
left by evaporating the lixivium to dryness in iron kettles, 
is the potash of commerce. This is moderately calcined to 
burn off the coloring matter, when a spongy mass of a fine 
light blue color is left, which is the pearlash. 

506. The pure carbonate is best obtained by calcining 
the cream of tartar, (acid tartrate of potash,) and dissolving 
out the carbonate from the coaly mass by water. The 
filtered solution is evaporated to dryness in a silver cap- 
sule, and the salt obtained pure. 

The carbonate of potash has a strong alkaline taste, 
turns cabbage or dahlia paper green, and is somewhat 
caustic; it dissolves in about twice its weight of water, 
forming a solution, which is much used in the laboratory. 
It crystallizes with difficulty, and takes up two equivalents of 
water in so doing. It is quite insoluble in alcohol. This is 
a very deliquescent salt, and must be kept in well-stopped 
bottles. 

Even when most pure it is apt to contain a trace of silica, 
from which it can be freed by igniting the bicarbonate, and 
evaporating its solution to dryness. 

Several samples of American potash examined by Dr. L. 
C. Beck yielded 73-6; 74-6 ; 75 and 76-9 per cent, of car- 
bonate and hydrate of potash; from 6 to 15 per cent, of 
chlorids of potassium and sodium; with from 1 to 15 per 
cent, of insoluble matter.* 
w 507. Bicarbonate of Potash, (KO, C0 2 + HO C0 2 ,) 

What crude forms of it do we know ? How is the crude article 
prepared? How does pearlash differ from potash? 506. How is 
the pure carbonate obtained ? What are its properties ? What did 
the samples of American potash examined by Dr. Beck yield ? 
50^. What is the bicarbonate of potash ? 

* Beck's Manual of Chemistry, p. 228, 2d edition. 



SALTS OF POTASH. 289 

Equiv. 100*1 9. — This salt is formed by passing a stream of 
carbonic acid gas through a cold solution of carbonate of pot- 
ash. It crystallizes in large and beautiful crystals referable 
to the right rhombic system. Four parts of water dissolve 
it; the solution has an alkaline taste and reaction, but is not 
caustic ; by heat it is converted to the simple carbonate, and 
it loses a portion of carbonic acid by solution in hot water. 

508. Sulphate of Potash, KO S0 3 , Equiv. 87*28.— This 
salt is usually prepared by neutralizing the residue of the nitric 
process, (312,) and is also procured by saturating a concen- 
trated solution of potash by strong sulphuric acid, added drop 
by drop. It is an anhydrous, well crystallized salt, which 
decrepitates with heat, and has a density of 2-4. It requires 
100 parts of water to dissolve 8*36 parts of this salt at 32°, 
and 0*096 parts more of the salt dissolve for every degree 
above that. 

509. Bisulphate of Potash, or Hydrate of Bisulphate, 
(sulphate of water and potash,) KO, S0 3 -f-HO, S0 3 , Equiv. 
136-37. — This salt is obtained by decomposing nitrate of po- 
tassa by two equivalents of oil of vitriol, in the process for 
nitric acid. It cools into a white crystalline mass at 386 0, 6, 
which is very soluble in water, with partial decomposition. 
It is dimorphous in crystalline form, one of its figures being 
identical with crystallized sulphur. The solution is strongly 
acid, and acts on bases nearly as powerfully as if potash 
were not present. 

510. Sesquisulphate of Potash, 2KO, S0 3 + HO, S0 3 .— 
This salt is obtained from the nitric acid residue, in long silky 
needles, which resemble asbestus. They cover the previous 
salt after long standing, with a beautiful vegetation or efflo- 
rescence. 

511. Nitrate of Potassa ; Saltpetre; Nitre; KO, N0 5 , 
Equiv. 101*25. — This important salt is a natural product in 
the hot and dry regions of India and South America, being 
formed by the gradual decomposition of animal matters in 
the soil. It is also formed artificially by heaping together 
beds of old mortar, earth, dung, and other animal matters, 



Give its formula. What are its properties ? 508. What formula 
has sulphate of potash ? How is it prepared ? 509. Give the for- 
mula of bisulphate of potash and its properties. 510. What is ses- 
quisulphate of potash? 511. Where is the nitrate of potash found ? 
How is it formed artificially ? 
25 



290 METALLIC ELEMENTS. 

and occasionally wetting the mass with fermenting urine. 
In some of the caverns in Kentucky, the soil on the floors 
becomes strongly impregnated with nitrate of lime, which is 
decomposed by wood ashes, and yields nitrate of polassa. 
In all these cases, the nitre is obtained by lixiviating the 
nitrous earth with water, evaporating and crystallizing the 
solution, redissolving and crystallizing a second time, until 
the salt is obtained pure. 

512. Properties. — Nitre crystallizes in long, six-sided 
prisms, with dihedral summits, derived from the right rhom- 
bic prism ; is anhydrous, and fusible at a heat under redness. 
It is unaltered in the air, and insoluble in alcohol, but dis- 
solves in about 3 parts of water at 60°. In hot water it is 
much more soluble, 100 parts of water at 206 o, 6, dissolving 
236 parts of the salt. Its solution has a cooling taste, and 
antiseptic properties. 

513. The great quantity of oxygen contained in nitre, and 
the ease with which it parts with it, render it a valuable 
agent. It is the chief constituent of gunpowder, imparting 
oxygen to the carbon and sulphur in that compound, to form 
with explosive energy those gases which are generated by the 
combustion of the materials. It is also much used in all 
pyrotechnic mixtures, as well as to deflagrate and scorify 
metals. The surface of silver ware is often scorified by 
nitre, which burns out the alloyed copper, and leaves a sur- 
face of pure silver. Good gunpowder is composed very 
nearly of 1 equivalent of nitre, 3 of carbon, and 1 of sul- 
phur. Thus : 



Theoretical mixture. 


English. 


Prussian. 


Sulphur, 11-9 


12-5 


11-5 


Charcoal, 13-5 


12-5 


13-5 


Nitre, 74-6 


75- 


75- 



Much of the explosive energy of gunpowder depends on 
its granulation ; a fine dust of the same composition with 
powerful powder, burns with a rapid deflagration, but with- 
out explosion. The gases formed from its combustion are 
carbonic acid and nitrogen, while sulphuret of potassium 

How is it procured from the nitrate of lime ? 512. What are the 
properties of nitre ? 513. What renders nitre a valuable reagent ? 
Of what is it the chief constituent ? What is the constitution of 
gunpowder ? On what does its explosive energy depend ? What 
are the products of its combustion ? 



SALTS OF POTASH. 291 

remains as a solid residue. The combustion of a squib, or 
moist gunpowder, gives a much more complicated result ; 
nitric oxyd, sulphureted hydrogen, carbonic acid, carbonic 
oxyd, nitrogen, and other products being formed. The con- 
stitution of gunpowder is varied according to the use for 
which it is intended. Thus, 20 sulphur, 15 charcoal, and 
65 nitre, are used for blasting-powder, and its combustion is 
rendered still slower by mixing it with several times its bulk 
of saw-dust. The effect then is more powerful in moving 
large masses of rocks. 

514. Nitrate of potassa has been much used in England 
as a manure, and, as already mentioned, (312,) is the source 
of the best nitric acid. It is also employed (254) to yield 
oxygen gas. 

515. Chlorate of Potash, KO, C10 5 , Equiv. 122.60.— 
This is the salt already named (253) as the best source of 
pure oxygen gas, of which it yields a great quantity by heat. 
It is formed by passing chlorine gas through a strong solu- 
tion of carbonate of potash, chlorate of potash and chlorid 
of potassium being formed, the chlorate being easily crys- 
tallized out by its less solubility than the chlorid of potassium. 
The reaction is between 6KO,C0 2 -fCl + 5KCl=KO, C10 5 . 

516. Properties. — Chlorate of potash crystallizes in flat 
tables referable to the oblique rhombic prism, and has a 
pearly lustre. In cold water (30°) it is very little soluble, 
and 100 parts of water at 60° dissolve only 6 parts of the 
salt. Its taste is cooling and disagreeable, resembling nitre. 
It fuses below redness ; oxygen is given ofT, and chlorid of 
potassium left behind. 

517. With combustible bodies its action is more ener- 
getic than that of nitre. With sulphur and charcoal it forms 
a compound that explodes by friction, and was formerly 
much used in the manufacture of lucifer matches. With 
sulphur alone, it detonates powerfully when wrapped in a 
paper and struck by a hammer. With phosphorus its reac- 
tion is extremely violent ; a deafening explosion follows the 
slightest compression of the ingredients, and burning phos- 
phorus is projected in all directions. 



If wet, what are they ? How is blasting-powder made more 
efficient ? 514. What other uses of nitre ? 515. What is chlorate 
of potassa, and how formed ? 516. What are its properties ? 517. 
What is its reaction with combustibles ? 



292 METALLIC ELEMENTS. 

All attempts to form a gunpowder of chlorate of potash 
have failed, the action of the mixture being so violent as to 
rend asunder the arms employed. A mixture of sugar and 
chlorate of potash is instantly inflamed by a drop of sulphu- 
ric acid. 

16. SODIUM. 

Equivalent, 23*27. Symbol, Na. (Natrium.) Density, -972. 

518. Sodium was discovered by Davy soon after the dis- 
covery of potassium, and in the same way. It is now pre- 
pared by a process quite similar to that already described (489) 
for potassium ; the carbonate of soda being used in place of 
the carbonate of potassa. 

This metal forms more than 40 parts in 100 of common 
salt, and is also frequent in various combinations in the min- 
eral kingdom. The ashes of sea-plants afford, in place of the 
carbonate of potash of land-plants, crude carbonate of soda. 

519. Sodium is a white metal, with a silvery brillianey, 
and much resembles potassium in its general properties. Its 
density is -972, and it melts at 194°. At common tempera- 
tures it is much harder than potassium, but is easily moulded 
in the fingers. It does not inflame on cold water, but moves 
about rapidly in a brilliant sphere, until it is all consumed. 
It may be alloyed with potassium by simple pressure, and is 
then inflamed on water, or alone on hot water, burning with 
a bright yellow light, characteristic of sodium. The same 
color is seen when a piece of soda-glass, or any mineral con- 
taining soda, is held in the flame of the blowpipe ; the flame 
is instantly tinged yellow. Exposed to the air, sodium soon 
falls to a white powder of oxyd of sodium. 

The compounds of sodium are so similar to those of po- 
tassium, that we can pass them with a brief notice. 

520. The Oxyd of Sodium, NaO, Equiv. No. 31-27, is 
formed by decomposing the carbonate, by the same means 
employed to form the caustic potash, (493.) It is a strong 
alkali, and very caustic. All its salts are soluble, by which 
it is distinguished from potash, whose chlorid forms a sparingly 
soluble compound with chlorid of platinum. 



Can gunpowder be made from it ? 518. Who discovered sodium, 
and how is it prepared ? 519. What are its properties ? 520. What 
is its oxyd ? How is it distinguished ? 



sodium. 293 

521. Chlorid of Sodium; Sea Sail; Common Salt; 
NaCl, 58-68. — This familiar and abundant salt is too well 
known to need much description. It is formed when sodium 
burns in chlorine gas, as well as when soda or its carbonate 
is neutralized by hydrochloric acid. Common salt forms 
about 27 of every 1000 parts of sea-water, and in warm 
climates, especially in the West Indies, sea- water is evapo- 
rated in large quantities by the sun's heat, to obtain salt. 
Numerous saline springs are found in New York, Ohio, Ken- 
tucky, and other places in this country, (457,) which afford 
vast quantities of salt by evaporation. The brine springs in 
Onondaga county, N. Y., are among the most valuable, and 
have been worked since 1789. This water contains one 
seventh part of dry salt. 

522. Common salt crystallizes in cubes, which are anhy- 
drous, and crackle or decrepitate when heated. It requires 
2*7 parts of water for its solution, and is equally soluble in 
hot and cold water. Its density is 2*557, and in pure alco- 
hol it is scarcely at all soluble. It fuses at redness, and 
sublimes in vapor at a higher temperature. It is employed 
for this reason to glaze earthen ware, since its vapor is de- 
composed by the oxyd of iron of the clay, chlorid of iron 
being driven off, while soda unites with the silica of the clay 
to form the glaze. 

The Bromid and Iodid of sodium resemble the correspond- 
ing compounds of potassium, and like them crystallize in 
cubes. 

523. Carbonate of Soda is manufactured on a very great 
scale from common salt, (421,) and is found nearly pure in 
the arts. It crystallizes in oblique rhombic prisms, with ten 
atoms of water of crystallization, (NaO,C0 2 + 10HO.) 
This salt is sometimes found native. The common form of 
carbonate of soda is a dry powder, called soda ash, which is 
an impure mixture of chlorid, sulphate, &c. The pure salt 
has 5S-58 per cent, of soda, and 41*42 of carbonic acid. 
Carbonate of soda dissolves in about five parts of water, aod 
the solution has a disagreeable alkaline taste. 

524. Bicarbonate of Soda, HO,C0 2 + NaO,C0 2 , Equiv. 

521. Describe common salt. How is it procured ? How mu~h 
does sea-water contain ? 522. Give the properties of salt. How 
does it act as a glaze ? 523. From what is carbonate of soda chiefly 
made ? What are its properties and constitution ? 524. How does 
the bicarbonate differ from the carbonate of soda ? 
25* 



294 METALLIC ELEMENTS. 

84*27. — This salt is formed when carbonic acid is passed 
through a saturated solution of the neutral carbonate. It i^ 
deposited in a dry white powder, which requires 13 times its 
weight of cold water to dissolve it. Its taste is alkaline, but 
much less disagreeable than the pure carbonate. It is much 
used in medicine and in domestic economy. 

This salt is thrown down as a granular precipitate, when 
bicarbonate of ammonia is added in fine powder to a solution 
of an equal weight of common salt. 

The sesquicarbonate of soda, (trona,) (2NaO-j-3C0 2 + 
4HO,) occurs in nature, being found in Africa and South 
America. It is little soluble, and unalterable in the air, and 
crystallizes in right rhomboidal prisms. 

525. Sulphate of Soda, Glauber's Salt, NaOS0 3 + 10HO, 
Equiv. 71*36 + 90.— This salt is the result of the hydrochlo- 
ric acid- process, (418,) and is also found native, and in 
solution in natural waters. It fuses by heat in its own 
water of crystallization, and loses its water (effloresces) in 
dry air, and falls into a white powder. Water dissolves half 
its own weight of sulphate of soda at 91°, but only 42.65 
parts at the boiling temperature. 

A saturated solution may be cooled under a film of oil, or 
in a vessel corked tight while hot, and when it is cold no 
crystals will be deposited until the air strikes the surface, or 
a small crystal is dropped into the solution, when the whole 
mass instantly becomes solid. This salt is much used in 
medicine as an aperient. 

526. The great use of sulphate of soda is in forming soda 
ash, or crude carbonate of soda, 
for the use of glass-makers and 
soap-boilers. For this purpose 
the sulphate is strongly heated in 
a reverberatory furnace, mixed 
with charcoal or coke, and car- 
bonate of lime. The sulphate is 

decomposed, sulphuret of calcium and carbonate of soda 
being formed ; the latter is dissolved out by hot water, and 
purified by crystallization. 



What are its properties ? What is the sesquicarbonate ? 525. 
Give the composition of sulphate of soda. What of its solubility ? 
How does its saturated solution act if cooled away from contact with 
the air ? 526. What is the chief use of sulphate of soda ? 




COMPOUNDS OF SODIUM. 295 

527. Nitrate of Soda, Soda Saltpetre; NaO,N0 5 .— This 
^alt is found in India and South America, where extensive 
plains are covered by it, as at Tarapaca in Chili, and Iquique. 
It resembles nitrate of potassa, but cannot be used to replace 
that salt in gunpowder, on account of its strong disposition to 
attract water from the air and grow damp. It is generally 
employed however in making nitric acid, and also as a fertil- 
izer in agriculture. 

This is a white salt, crystallizing in rhombs, specific grav- 
ity 2-09, very soluble, with a cooling taste, and deflagrates 
on burning coals with a strong yellow light. 

528. The phosphates of soda are a very interesting and 
important class of salts, the study of which has done much 
to advance our knowledge of theoretical chemistry. We 
will mention five phosphates of soda, three tribasic, one bi- 
basic, and one monobasic phosphate. 

Phosphate of Soda. — Common Tribasic Phosphate, 2NaO 
HO,P0 5 + 24HO.— This beautiful salt is prepared by pre- 
cipitating the acid phosphate of lime, (317,) with a slight 
excess of carbonate of soda. It crystallizes in oblique 
rhombic prisms, which are efflorescent. The crystals dissolve 
in four parts of cold water, and undergo the aqueous fusion 
when heated. The salt has a pleasant saline taste, and is 
purgative ; its solution is alkaline to test-paper. 

A second tribasic phosphate, sometimes called subphos- 
phate, 3NaO, P0 5 + 24HO, is obtained by adding solution of 
caustic soda to the preceding salt. The crystals are slender 
six-sided prisms, soluble in 5 parts of cold water. It is de- 
composed by acids, even the carbonic, but suffers no change 
by heat, except the loss of its water of crystallization. Its 
solution is strongly alkaline. 

A third tribasic phosphate, often called superphosphate 
or Diphosphate, NaO,2HO,P0 5 + 2HO, may be obtained by 
adding phosphoric acid to the ordinary phosphate, until 
it ceases to precipitate chlorid of barium, and exposing the 
concentrated solution to cold. The crystals are prismatic, 
very soluble, and have an acid reaction. When strongly 



527. What is said of nitrate of soda ? What is its constitution and 
use ? 528. What is said of the phosphates of soda, and how many 
are named ? Give the composition and properties of common phos- 
phate of soda. What is the composition of the subphosphate ? What 
that of the third tribasic phosphate ? 



296 METALLIC ELEMENTS. 

heated, the salt becomes changed into monobasic phosphate 
of soda. 

529. Microcosmic Salt, or Phosphate of Soda and Am- 
monia, (HO,NH 4 0,NaO,P0 5 + 8HO,) is much used in blow- 
pipe operations as a flux. It is formed by dissolving with a 
gentle heat, 1 part of chlorid of ammonium and 6 or 7 parts 
of phosphate of soda, in 2 of water. Chlorid of sodium is 
formed, and the microcosmic salt crystallizes out in rhombic 
prisms, which lose 8HO by heat. 

530. Bibasic Phosphate of Soda, Pyrophosphate of Soda, 
2NaO, P0 5 -f 10HO. — Prepared by strongly heating common 
phosphate of soda, dissolving the residue in water, and re- 
crystallizing. The crystals are very brilliant, permanent in 
the air, and less soluble than the original phosphate ; their 
solution is alkaline. A bibasic phosphate, containing an equiv- 
alent of basic water, has been obtained ; it does not, however, 
crystallize. 

531. Monobasic Phosphate of Soda, Metaphosphate of 
Soda, NaO, P0 5 . — Obtained by heating either the acid tri- 
basic phosphate, or microcosmic salt. It is a transparent, 
glassy substance, fusible at a dull red-heat, deliquescent, and 
very soluble in water. It refuses to crystallize, and dries up 
in a gum-like mass. 

The tribasic phosphates give a bright yellow precipitate 
with a solution of nitrate of silver; the bibasic and monobasic 
phosphates afford white precipitates with the same substances. 
The salts of the two latter classes, fused with excess of car- 
bonate of soda, yield the tribasic modification of the acid. 

532. Borax; Biborate of Soda ; NaO, 2BO 3 + 10HO.— 
Borax crystallizes in right rhomboidal prisms, which are solu- 
ble in 15 or 16 parts of water; the solution has an alkaline 
reaction and sweetish alkaline taste. It loses its water by 
heat, and being very fusible, is much used in metal lurgic 
processes and as a blowpipe reagent. It is entirely procured 
from natural sources of boracic acid already mentioned, 
(367,) and from the waters of several lakes in Thibet which 
contain it. j 



When heated, this salt becomes what ? 529. "What is the micro- 
cosmic salt? How is it formed? 530. How is bibasic pi- -sphate 
formed? What is its formula? 531. What is the composition of 
the monobasic phosphate of soda ? What are the reactions of the 
phosphates of soda with tests ? 532. Give the composition of borax. 
What is its use / 



sorai/M. 297 

Manufacture of Glass. 

i 

533. Silicates of Soda. — Both soda and potash form 
compounds with silicic acid (361) by fusion, which are 
silicates, but of uncertain composition. If 4 parts of the 
alkali are used to 1 of the silica, the glass is soluble, but 
whatever may be the proportions used, the resulting silicate 
is always an uncrystalline, homogeneous, transparent mass. 
The " soluble glass" formed by fusing together 8 parts of 
carbonate of soda (or 10 of carbonate of potash) with 15 
parts of pure sand and 1 of charcoal, is insoluble in cold, 
but dissolves in 4 or 5 parts of hot water, forming a sort of 
varnish, which may be applied to wood or manufactured 
stuffs, which are to a good degree protected by it from the 
action of fire. 

534. Glass is a variable compound of the silicates of pot- 
ash, soda, lime, and alumina, with oxyds of lead and iron, 
fused together by a very high and long-continued heat, in 
proportions suited to the object for which the glass is to be 
used. This is not the place to describe the varied and inter- 
esting manipulations by which the fused material is blown, 
cast, moulded, or pressed into the countless forms of utility 
and ornament, which the wants of society demand. A visit 
to a large glass-house is always full of instruction and plea- 
sure. 

535. Window-glass is a silicate of soda and lime, which 
requires an intense heat for its fusion, and forms a very 
hard and brilliant glass. Plate glass, such as is used for 
mirrors, crown glass employed for glazing, and the beautiful 
Bohemian glass, are all silicates of potash and lime. 

Crystal glass is formed by fusing together 120 parts of 
fine sand, 40 purified potash, 36 of litharge or minium, (oxyd 
of lead,) and 12 of nitre. This forms a very fusible glass, 
easily worked, and so soft as to be cut and polished, with 
comparative ease. 

Green bottle glass is usually a silicate of alumina, with 
oxyds of iron and magnesia, and potash or soda. It is 
formed of the cheapest refuse of the soap-boiler's waste, and 
lime which has been used to make caustic potash or soda. 

533. What is said of the silicates of soda ? What is the soluble 
glass? 534. What is glass ? 535. What is window and plate glass? 
What is crystal glass ? Bottle glass ? 



298 METALLIC ELEMENTS. 

All glass must be carefully annealed after it is made, by 
slow cooling, or it will break in pieces with the least scratch 
or jar. Slow cooling of heated glass for many hours, or 
even days, for heavy articles, renders the mass homogeneous 
and less brittle. 



17. AMMONIUM. 

Eqidvalent, 18.06. Symbol, NH 4 , (hypothetical.) 

536. Ammonium, (NH 4 .) — This compound of hydrogen 
and nitrogen has never been isolated, though we have 
reason to believe in its existence. When a solution of am- 
monia, or of sal-ammoniac, is electrolized, nitrogen escapes 
at the + side and hydrogen at the — side ; but if the latter 
pole is made by using a portion of mercury, no hydrogen is 
evolved, but the mercury swells up, loses its fluidity, becomes 
like soft butter, and gradually attains many times its original 
bulk, having the lustre and general character of an amalgam. 
A more simple mode of, forming this amalgam, consists in 
making a little potassium or sodium combine by heat, with 
about 1 00 times its weight of metallic mercury. This alloy, 
when placed in a strong solution of sal-ammoniac, begins at 
once to increase in volume by the formation of the ammoni- 
acal amalgam, until it has attained very many times its origi- 
nal bulk, and has a pasty, butyraceous consistence. 

When the alloy of potassium is placed in hydrochloric acid, 
the alkaline metal decomposes the acid, forming chlorid of 
potassium and evolving hydrogen. If we substitute for the 
acid (chlorid of hydrogen) a solution of chlorid of zinc, 
ZnCl, a like decomposition ensues ; but the zinc, instead of 
being set free like the hydrogen, combines with mercury to 
form an amalgam. The present reaction is precisely similar ; 
chlorid of ammonium, NH 4 C1, being substituted for the chlo- 
rid of zinc ; the ammonium which is liberated, combines with 
the mercury and forms the light pasty amalgam. It crystal- 



What treatment does all glass require to make it fit for use ? 536. 
What is ammonia and how formed ? What more simple mode of 
forming the ammoniacal amalgam is also described ? How does the 
alloy of mercury and potassium act in hydrochloric acid ? How if 
we substitute chlorid of zinc for the acid ? What amalgam is then 
formed ? Explain this reaction. 



AMMONIUM. 2b3 

lizes in cubes at 32°, whereas pure mercury is fluid even at a 
temperature of —39° F. It is evident that it has combined 
with something which has given it new properties^ This is 
supposed to be the metallic radical ammonium. The spongy 
mass, as soon as the electric action ceases, rapidly suffers 
decomposition. Ammonia and hydrogen are set free in the 
proportion of 1 to 2, and the mercury regains its original 
state unaltered. Berzelius and other able chemists explain 
this reaction, on the ground that the ammonia, by gaining an 
additional equivalent of hydrogen, assumes the peculiar 
character of a metal, and unites with mercury, forming an 
amalgam. This hypothetical metal can replace potassium 
and sodium perfectly in combination, and is therefore isomor- 
phous with them. All the salts of ammonia are, on this 
view, derived from this radical, and its union with the second 
class gives us a series of bodies analogous to the chlorids, 
bromids, &c, of the other electro-positive bases. 

Salts of Ammonium. 

537. Chlorid of Ammonium; Sal Ammoniac, NH 4 C1. — 
This salt occurs in nature, sometimes quite pure, as at De- 
ception Island, and in volcanic districts generally. It was 
originally prepared in Egypt, by sublimation from the soot 
of the burnt camel's-dung. It is also obtained largely from 
the ammoniacal waters of the gas-works. It is purified by 
evaporating the crude solutions to dryness, after treating 
them with a slight excess of hydrochloric acid to neutralize 
the free ammonia, and subliming the dry mass in iron vessels. 

It has a sharp saline taste, corrodes metals powerfully, is 
soluble in three parts of cold water, and crystallizes from its 
solution in octahedrons. The sublimed salt has a fibrous 
texture, and is very tough and difficult to pulverize. 

The formation of this compound is easily shown by using 
the apparatus already figured, (435,) with hydrochloric acid 
in one flask and strong ammonia water in the other ; the 
commingling of the dry gases, driven over by heat to the 
central bottle, fills it with a white cloud of sal ammoniac, 
CIH + NH 3 =C1NH 4 . 



What are its properties ? What does its decomposition yield ? 
In this view how are the ammoniacal salts constituted ? 537. How 
is sal ammoniac found in nature, and how formed artificially ? What 
are its properties ? How is its formation illustrated in the class- 
room ? Give the reaction. 



300 



METALLIC ELEMENTS. 




538. Sulphuret of Ammonium and Hydrogen, (hydro- 
sulphuret of ammonia,) NH 4 S-fHS. — This very useful 
compound is formed by passing a long-continued, slow cur- 
rent of sulphureted hydrogen from the gas-bottle (a) through 

the bottles d, e,f, 
g, filled with 
strong water of 
ammonia. This 
arrangement is a 
simple form of 
Woulfe's bottles, 
(442.) A single 
Dottle of ammonia, 
(as b) is sufficient 
for all common 
purposes. It should be kept cold. The ammonia absorbs an 
enormous quantity of the gas, and the resulting sulphuret, 
which has the strong odor of the gas, is colorless at first, but 
gradually assumes a yellow color. It is an invaluable reagent 
as a precipitant of the metals, and is also used in medicine. 

There are several simple sulphurets of ammonium, but 
they are of no particular interest. 

539. Sulphate of Ammonia, or Sulphate of Oxyd of 
Ammonium, NH 4 0, S0 3 + HO. — This salt, which is a power- 
ful fertilizer, is procured in the large way by neutralizing 
the ammoniacal liquor of the gas-works by sulphuric acid : 
or it may be easily obtained pure by neutralizing dilute sul- 
phuric acid with carbonate of ammonia. 

540. Carbonates of Ammonia. — There are* several of 
these salts. The common white sal-volatile of the shops, 
with a pungent smell and alkaline reaction, is nearly a ses- 
quicarbonate, (2NH 4 0,3C0 2 .) Exposed to the air, this salt 
becomes a white inodorous powder, which is a bicarbonate. 
The sesquicarbonate is a very valuable salt to the chemist, 
and forms the basis of the smelling-bottles so much in use. 
The dry white powder formed by the contact of dry carbonic 
acid and ammonia in an apparatus like that before used, 
(435,) is a neutral anhydrous carbonate, (NH 3 , C0 2 ,) very 
pungent, volatile, and dissolving readily in water. 



538. How is sulphuret of ammonium formed ? What is its com- 
position? What its properties and uses ? 539. What is the composi- 
tion of sulphate of ammonia ? 540. What carbonates of ammonia 
are named ? What is the sal-volatile ? What is the inodorous salt ? 



BARIUM. 301 

541. Nitrate of Ammonia, or Nitrate of Oxyd of Am- 
monium, (NH 4 0, N0 5 .) — This salt has already been noticed 
(305) under the description of nitrous oxyd. Its crystals 
resemble nitre, deliquesce in moist air, and dissolve in 2 parts 
of cold water, the solution sinking the thermometer to zero, 
(111.) It deflagrates on burning coals like nitre. 

542. All the ammoniacal salts are volatilized by a high 
temperature, yield the ammoniacal odor by trituration with 
caustic potassa or lime, only boiling with solutions of potash. 
They are all soluble, and give a sparingly soluble, yellow, 
crystalline precipitate with chlorid of platinum. 

18. LITHIUM. 

Equivalent, 6*43. Symbol, L. 

543. This very rare metal is a constituent of several 
minerals, as spodumene, ' petalite, lithia-mica, &c, from 
whose decomposition by a particular process, hydrate of 
lithia is obtained, the electrolysis of which afforded Davy a 
white oxydizable metal analogous to sodium. Its atomic 
number is far below that of any other metal, and only carbon 
and hydrogen are lower in the scale of equivalents ; this 
gives its oxyd a very high power of saturating acids. 

The oxyd (LO) is an alkali, but much less soluble than 
potash and soda. Its sulphate is a beautiful salt, and gives a 
rosy flame to alcohol. The lithia compounds all give this tint 
to the outer flame of the blowpipe. Its name is from lithos, 
a stone, in allusion to the natural origin of this alkali. 



CLASS II. METALS OF THE ALKALINE EARTHS. 

19. BARIUM. 

Equivalent, 68.55. Symbol, Ba. 

544. Barium is a silver-white malleable metal, which is 
easily oxydized, and melts below a red heat. It was pro- 

541. Describe the nitrate of ammonia. How does it affect the 
thermometer while dissolving? 542. How are the ammoniacal 
salts characterized ? 543. What is the equivalent of lithium ? In 
what minerals is it found ? How is its oxyd characterized ? What 
property have all the lithia compounds ? 544. What is barium ? 
26 



302 METALLIC ELEMENTS. 

cured by Davy by a process similar to that which yielded 
potassium, &c. It is better obtained by passing vapor of 
potassium over baryta (oxyd of barium) heated to redness in 
an iron tube. Mercury dissolves out the reduced metal, and 
the amalgam is then distilled. 

545. Baryta, or Protoxyd of Barium, BaO. — Baryta is 
best obtained by decomposing the nitrate at a red heat. It is 
a dry, gray powder, which combines with water to form a 
hydrate, slaking with the evolution of great heat and even 
light. The hydrate dissolves in two parts of hot water, or 
twenty of cold, and crystallizes in flat tables. The aqueous 
solution is a valuable reagent. 

Sulphate of baryta, or heavy spar, is found abundantly as 
an associate of other minerals in veins ; and from it, or the 
native carbonate of baryta, all the artificial compounds of 
barium are formed. 

546. The Peroxyd of Barium, Ba0 2 , is formed by pass- 
ing pure oxygen gas over the oxyd heated to redness in a 
porcelain tube. It is chiefly interesting as being the means 
of procuring the peroxyd of hydrogen, (410.) 

Chlorid of Barium, BaCl + 2HO. — This salt occurs in 
white tabular crystals, containing two equivalents of water 
which are expelled by heat. It dissolves in a little more than 
twice its weight of cold water, and the solution is a valuable 
reagent for detecting the presence of sulphuric acid. 

547. The Nitrate of Baryta, (BaO, N0 5 0) is also a solu- 
ble white salt, which crystallizes in anhydrous octahedrons, 
and dissolves in eight parts of cold or three parts of hot water. 
Both it and the chlorid are prepared by dissolving the native 
or artificial carbonate in the proper acid. 

Sulphate of Baryta — Heavy Spar, (BaO, S0 3 ,) is a mine- 
ral found abundantly in many places in this country, as at 
Cheshire, Ct. It crystallizes in tabular modifications of the 
rhombic prism, often very beautiful. It is also found mas- 
sive at Pillar Point in N. Y. Its high specific gravity (4-3 
to 4*7) gives it the name of heavy spar. It is quite insoluble 
in water or acids, and not easily decomposed. When strongly 

How obtained ? 545. From what substances are the barium salts 
formed? Characterize baryta and its action with water. 546. How 
is peroxyd of barium formed, and for what used ? Give the charac- 
ters of the chlorid of barium. For what is it a test ? 547. How is 
the nitrate of baryta characterized ? How is heavy spar found in 
nature ? 



STRONTIUM. > 303 

heated with charcoal powder, however, it^suffers decompo- 
sition, (BaO, S0 3 -f-4C = BaS + 4CO) ; carbonic oxyd is 
given off, and the soluble sulphuret of barium may be dis- 
solved out from the coaly mass. 

Sulphate of baryta is extensively ground up as a pigment, 
being mixed with white lead as an adulteration. 

548. Carbonate of Baryta, BaO, C0 2 , or the witherite of 
mineralogists, is a mineral of some interest, and useful as the 
chief source of the various compounds of baryta. All the 
soluble baryta salts are poisonous, and their presence may 
always be detected by sulphuric acid, with which they form 
an insoluble sulphate. 

20. STRONTIUM. 

Equivalent, 43*78. Symbol, Sr. 

549. Strontium is obtained from its oxyd in the same 
manner as barium, and like it is a white metal, oxydized 
easily in air, and decomposing water at common tempera- 
tures. There are two oxyds, the protoxyd and the peroxyd 
of strontium, similar in properties to the like oxyds of barium. 
The sulphate of strontia, (celestine,) is a rather abundant 
mineral, and the carbonate (strontianite) is much esteemed 
by mineralogists. They are very similar in properties to 
the sulphate and carbonate of baryta. 

550. The Chlorid of Strontium (SrCl + 9HO) is a deli- 
quescent salt, soluble in two parts of cold water. It loses its 
water of crystallization by heat. Both it and the nitrate of 
strontia (SrO, N0 5 ,) are much employed by pyrotechnists in 
forming the red fire of theatres and fire-works. All the 
compounds of strontium give a peculiar red tint to the flame 
of the blowpipe, while the barytic salts do not. The salts of 
strontia are not poisonous. 

21. CALCIUM. 

Equivalent, 20. Symbol, Ca. 

551. Calcium is a yellowish white metal, obtained like 

Give its formula and properties. 548. What is carbonate of 
baryta ? What character have the soluble salts of baryta ? How is 
their presence detected ? 549. How is strontium obtained and how 
characterized ? What familiar salts of this metal are found native ? 
550. Describe the chlorid of strontium. What is it used for ? 551. 
What is calcium and how is it obtained ? 



304 * METALLIC ELEMENTS. 

barium, and has so strong a disposition to combine with oy , 
gen that it is difficult to observe its properties. 

552. Protoxyd of Calcium — Lime, CaO. — This most 
valuable substance, so well known as quick lime, is procured 
in a state of great purity by heating the stalactites from 
Scoharie Cave, N. Y., or Weir's Cave, Ya., in a close cruci- 
ble for some hours. The carbonic acid and organic coloring 
matters are driven off, and pure white oxyd of calcium 
remains. This is an infusible, rather hard body, having a 
great affinity for carbonic acid and for water, with which it 
combines to form a hydrate, evolving great heat. The pre- 
paration of common mortar used in building illustrates this 
property on a large scale. The dry hydrate is a bulky pow- 
der, having one equivalent of water, which may be again ex- 
pelled by heat. It is soluble in about 500 parts of cold, and 
less so in hot water. The solution (lime water) is a very 
valuable reagent to the chemist, and is also used as an anta- 
cid in medicine. Exposure to air decomposes it, forming 
the carbonate of lime. The solution has^a strong, disagree- 
able alkaline taste, and changes vegetableyfolors. 

Common lime is prepared by heating limestone (carbon- 
ate of lime,) in large stone furnaces, filled from the top with 
the limestone and fuel ; the fire is kept up constantly, by 
renewed charges of the materials at top, while the prepared 
caustic lime is drawn out at the bottom. 

553. Mortar acts as a cement by the slow formation of a 
carbonate of lime, which binds together the grains of sand 
that make up the greater part of the mortar. The smaller 
the portion of lime used, the more firm will be the cement at 
last ; but it is then so much more difficult to work, that an 
excess of lime is usually employed. The presence of oxyd 
of iron and manganese, of alumina, magnesia, silica, and 
other like substances,^ a limestone gives the lime prepared 
from it the property of hardening under water, which is hence 
called hydraulic lime. 

Lime is much used in improved agriculture, as a manure. 
It acts to decompose vegetable matters, to neutralize acids, 
dissolve silica, and retain carbonic acid. It is always present 

What is its oxyd ? 552. How is quick lime prepared ? Give its 
properties. How does it act with water ? How much water dis 
solves it ? What is the solution used for ? How is common lime 
prepared? 553. What is the cause of the strength of mortar ? What 
is hydraulic lime ? What is said of the agricultural use of lime ? 



CALCIUM. 305 

naturally in every fertile soil, and is a constant ingredient in 
the ashes of most plants. 

554. Chlorid of Calcium, CaCl. — The solution of lime 
or its carbonate in hydrochloric acid to saturation, gives us 
this salt. It is when fused a white crystalline solid, with a 
great avidity for moisture, and for this reason it is used in the 
desiccation of gases, &c. It is soluble in alcohol, with 
which it forms a definite crystallizable compound. It forms 
a powerful freezing mixture with ice, (111.) 

The sulphurets and phosphurets of caicium have little in- 
terest. The phosphuret being decomposed by water, is an 
available source of the spontaneously inflammable phosphu- 
reted hydrogen. 

555. Sulphate of Lime — Gypsum — Selenite, CaO, S0 3 . 
—This salt in the form of hydrate (CaO,S0 3 -f 2HO) is 
abundant in nature, and is much used in agriculture as a 
manure, being ground to powder, and after expelling the 
water by heat, as a material for stucco and plaster casts. 
It is then commonly known as * plaster of Paris.' When 
crystallized in transparent flexible plates, it is called selenite. 
Anhydrous gypsum also is sometimes found native, and is 
known by the mineralogical name of anhydrite. Gypsum is 
frequently associated with rock-salt. It is soluble in about 
500 parts of water, and is present in most natural waters. 
By a heat of 200° to 300° it loses its water of composition, 
and when the anhydrous powder is moistened, the lost water 
is regained, and it becomes solid ; but if overheated, this re- 
sult does not happen. 

556. Fluorid of Calcium — Fluor Spar, CaF. — This is 
a rather abundant mineral, being found beautifully crystalliz- 
ed of various colors, in the cube and its modifications. It is 
the principal source from which we obtain the hydrofluoric 
acid, (425,) by decomposition with sulphuric acid. It often 
phosphoresces very beautifully with heat, and emits a green, 
yellow, or purple light, at a temperature below redness. 

557. Phosphates of Lime. — There are several phosphates 
of lime corresponding to the several phosphoric acids, (320, 

554. What is the chlorid of calcium ? For what is it used ? What 
is the phosphuret of calcium used for ? 555. Give the common 
names of sulphate of lime. For what is it used ? Give its proper- 
ties. On what does its use in stucco depend ? 556. What is fluor 
spar ? How is it found ? For what used ? What beautiful property 
has it ? 557. What phosphates of lime are known ? 
26* 



306 METALLIC ELEMENTS. 

325.) The earth of bones is a tribasic phosphate of lime, 
and the mineral known as apatite is also a phosphate of lime. 
The phosphates of lime are insoluble in water, but dissolve in 
dilute acids. All cereal grains, and many other vegetables, 
contain phosphate of lime in their ashes. 

558. Carbonate of Lime — Marble — Calcareous Spar, 
CaO, C0 2 . — This is one of the most abundant minerals of 
the earth, forming in limestone vast mountains and wide 
spread geological deposits. It occurs most superbly crystal- 
lized in rhombohedYal forms, which constitute brilliant orna- 
ments in mineralogical collections. It is soluble in dilute 
acids, with escape of carbonic acid, and is also decomposed 
by heat, (552,) leaving quick-lime. 

559. Chlorid of Lime — Bleaching -Powder. — This valu- 
able compound is formed when chlorine gas is gradually ad- 
mitted to hydrate of lime slightly moist and kept cool. The 
chlorine is absorbed largely, and the bleaching-powder of 
the arts is formed. It is a soft white powder, easily soluble 
in about 10 parts of water, giving a highly alkaline solution, 
which bleaches feebly. It is employed by dipping the goods 
in a weak solution of chlorid of lime, and then in very 
dilute sulphuric acid. The chlorine is thus evolved and 
does its work. Several repetitions are needed to complete the 
process. This compound emits a strong smell, which is 
similar to chlorine, but is due to hypochlorous acid ; it 
is very useful for disinfecting offensive apartments, and its 
energy is increased by the addition of a little acid. The dis- 
infecting liquid of Labarraque is a compound of chlorine with 
soda, similar in composition to solution of bleaching-powder. 

The chlorid of lime is now known to be a mixture of chlo- 
rid of calcium and hypochlorite of lime, (267.) 

22. MAGNESIUM. 

Equivalent, 12-67. Symbol, Mg. 

560. Magnesium is obtained by decomposing the chlorid 
of that metal heated to redness in a glass tube, by passing 

In what do we find phosphate of lime ? 558. What is said of car- 
bonate of lime ? What other names has it ? What is formed from 
it? 559. What is bleaching-powder ? How formed ? How employ- 
ed ? What is Labarraque's liquor ? What is the known composi 
tion of bleaching-powder ? 560. Give the equivalent and prepara- 
tion of magnesium. 



MAGNESIUM. 307 

over it the vapor of potassium or sodium. Chlorid of potas- 
sium or sodium is formed, and the metallic magnesium is 
separated by dissolving out the soluble chlorid. 

It is a white metal, malleable and brilliant. It fuses with 
a red heat, and if heated to redness in the air, burns with a 
brilliant light, becoming oxyd of magnesium. It does not 
tarnish in the air, and does not decompose water even at 
212°, but dissolves in acids with escape of hydrogen. 

561. Oxyd of Magnesium — Calcined Magnesia, (MO.) 
— This substance is left when the carbonate of magnesia is 
heated to redness. It is a white, earthy powder, insoluble in 
water, but readily dissolves in weak acids. It occurs in 
nature crystallized in regular octahedrons, forming the 
mineral periclase. It is much used in medicine as a mild 
and efficient aperient. The hydrate of magnesia (MgO,HO) 
is formed when magnesia is precipitated from its solutions 
by an alkali. Heat expels the equivalent of water. The 
hydrate is found beautifully crystallized in thin pearly plates 
at Hoboken, New Jersey. 

562. Chlorid of Magnesium, (MgCl.) — This salt is best 
prepared by neutralizing equal portions of hydrochloric acid, 
one with magnesia and the other with ammonia, mixing the 
two portions and evaporating to dryness. The dry mass is 
heated in a covered crucible as long as sal ammoniac is 
given off, when pure chlorid of magnesium is left. It is a 
very deliquescent salt, and supplies the means of procuring 
metallic magnesium. When magnesia is dissolved in hydro- 
chloric acid, a hydrated chlorid of magnesium results. By 
heat the water is expelled, carrying with it hydrochloric acid, 
and leaving pure magnesia behind. Chlorid of magnesium 
exists in sea-water. The iodid and bromid of magnesium 
are also soluble salts, but the fluorid is insoluble. 

563. Sulphate of Magnesia — Epsom Salts, (MgO, S0 3 
+ 7HO.) — This well known salt is easily formed by dis- 
solving magnesia or its carbonate in sulphuric acid. It is 
also found native at Corydon, Illinois. It is made on a large 
scale by dissolving serpentine rock in strong sulphuric acid. 



What are its properties ? 561. What is the oxyd of magnesium ? 
How is it used ? How found in nature ? 562. How is the chlorid 
of magnesium prepared ? Describe it. When magnesia is dissolved 
in hydrochloric acid, what happens ? 563. What is the composition 
of sulphate of magnesia ? How is it made in the large way ? 



308 METALLIC ELEMENTS. 

It is very soluble, and like all the soluble salts of magnesia, 
has a peculiar bitter taste. 

564. The Carbonate of Magnesia is found native in mag- 
nesian rocks, and is formed artificially by decomposing any 
of the soluble salts of magnesia by an alkaline carbonate. 
It is insoluble in water ; but a solution of carbonic acid dis- 
solves it, and forms the celebrated Murray's solution of 
magnesia ; it is decomposed by contact of air, carbonic acid 
escapes, and carbonate of magnesia is thrown down. 

Phosphate of soda with ammonia throws down a crystalline 
insoluble salt from magnesian solutions, which is the double 
phosphate of magnesia and ammonia. This is the most 
ready mode of testing for the presence of magnesia. 

565. Magnesia occurs abundantly in nature as a con- 
stituent of many minerals, as well as in the form of hydrate 
and carbonate. It is present in nearly all fertile soils, and 
constitutes an important part of the inorganic matters in the 
husk and seeds of many plants. The potato especially 
contains a large portion of the ammonio-phosphate of mag- 
nesia, and hence bran is a useful manure for the potato, 
because it is peculiarly rich in this salt. 



CLASS III.— METALS OF THE EARTHS. 

23. ALUMINIUM. AL. = 13*69. 

566. Aluminium is best obtained, like magnesium, by the 
action of sodium or potassium on its chlorid. It is a gray 
powder, not easily melted, has a metallic lustre, and burns 
when heated in the air with a bright light, forming alumina. 

567. Alumina ; Sesquioxyd of Aluminium ; A1 2 3 . — 
Pure alumina is found crystallized in those precious gems, 
the oriental ruby and sapphire, which are next in hardness 
and value to the diamond. Emery is also nearly pure alu- 
mina. Alumina is an abundant ingredient in many other 
minerals, and forms a large part of many slaty rocks, from 
whose decomposition clays are produced. 



564. What is carbonate of magnesia ? What is Murray's solution ? 
What test have we for magnesia ? 565. How does magnesia occur 
in nature ? In what plants is it found ? 566. How is alumina ob- 
tained ? What are its properties ? 567. What is the formula of 
alumina ? In what is it found pure ? 



ALUMINA. 309 

Pure alumina is a fine white powder, not rough and gritty 
like silica ; mixed with water it forms a plastic mass, which 
has the well known tenacious qualities of clay. It is the 
basis of the art of pottery. When alumina is precipitated 
from its solutions in acids by an alkali, it falls as a bulky, 
gelatinous, transparent hydrate, which shrinks very much on 
drying, and has three equivalents of water of composition at 
100°, which are expelled by heat. The anhydrous alumina 
is almost insoluble in acids, while the hydrate is readily dis- 
solved, forming salts of a peculiar astringent taste, familiarly 
known in common alum. 

Alumina is precipitated as a hydrate from solution, by 
either potash, soda, or ammonia, and their carbonates ; an 
excess of the two first will redissolve the precipitate. Hy- 
drosulphuret of ammonia throws down alumina. The chlorid 
of aluminium has no particular interest except as a means of 
procuring the metal. 

568. Sulphate of Alumina, Al 2 3 3S0 3 +18HO. — This 
salt is prepared by saturating dilute sulphuric acid with 
alumina ; it has a sweetish astringent taste, is soluble in 2 
parts of water, and crystallizes in thin plates. 

Alums. — Sulphate of alumina forms with potash, soda, 
and ammonia, double salts of much interest, called alums. 
They are all soluble salts, with a sweetish astringent taste, 
and crystallize in the regular system, or first class, (220,) 
usually as modified octahedrons, which have uniformly 24 
equivalents of water of crystallization. Common potash-alum 
has the formula Al 2 3 ,3S0 3 + KO,S0 3 + 24HO, (205;) it 
dissolves in 18 parts of cold water, and the solution has an 
acid reaction. 

569. Alum and Acetate of Alumina are largely employed 
in the arts of dyeing and tanning. Alumina combines with 
coloring matters, and seems to form a bond of union be- 
tween the fibre of the cloth and the color. In this it is said 
to act the part of a mordant. When alum is added to the 
solution of a coloring matter, and the alumina is precipitated 
with an alkali, all the coloring matter is thrown down with 

What are its properties ? How is its hydrate described ? What 
difference is there in the two forms of alumina ? How is alumina 
distinguished by tests ? 568. What is the sulphate of alumina ? 
What are alums? Give the formula of common alum. 569. In 
what art is alum much used ? How does it act with colors ? What 
are lakes ? 



310 METALLIC ELEMENTS. 

it and forms what is called lake. The common lake used 
in water-coloring is derived from madder treated in this way. 
Carmine is a lake made from cochineal. 

570. Silicates of Alumina. — This is the most extensive 
and important class of the aluminous salts, and comprises a 
great number of interesting minerals. Feldspar, (A1 2 3 , 
3Si0 3 + KO,Si0 3 ,) which is one of the chief components of 
granite and granitic rocks, is of this class, and has the com- 
position of an anhydrous alum, the sulphuric acid being 
replaced by the silicic. Kyanite and Sillimanite are simple 
basic silicates of alumina. Albite is a salt having soda in 
place of the potash in feldspar, while spodumene and petalite 
are similar compounds, with a portion of the soda replaced 
by lithia. Many other similarly constituted compounds are 
found among minerals, some of which are hydrous and others 
anhydrous, and varied by frequent substitution of peroxyd ot 
iron, or other isomorphous bases, for the alumina. 

571. Pottery. — The decomposition of feldspar and other 
aluminous minerals and rocks, gives origin to the clays 
which are so important in the art of pottery. Decomposed 
feldspar forms porcelain clay, commonly called kaolin. The 
undecomposed mineral is often ground up to mix with the 
materials for porcelain. The feldspar of Middletown, Ct., 
and Wilmington, Delaware, is used in large quantities for 
this purpose. 

The difference between porcelain and earthen ware, con- 
sists in the partial fusion of the materials of the former by 
the heat of the furnace, which gives it the semi-transparency 
and great beauty for which it is so highly prized. The 
glaze in porcelain is formed of a more fusible mixture of the 
same materials, put over the articles as a wash, after they 
have been once through the furnace ; (in which state they 
are called biscuit ware ;) they are then baked again at a heat 
which fuses the glaze, but which does not soften the body of 
the ware. 

572. The painting of porcelain is an art requiring a refined 
knowledge of chemistry. All the colors used in this art are 



570. What is the most important class of alumina compounds ? 
Give the composition and properties of feldspar. 571. What is the 
origin and composition of clays ? Of what material is porcelain 
composed ? How does it differ from earthen ware ? Of what does 
the glaze consist ? 



GLUCINUM, YTTRIUM, &C. 311 

metallic oxyds, which are put on after the Ware has been 
once baked. The colors result from compounds formed by 
the metallic oxyds with alumina by fusion, and do not ap- 
pear until after the baking. Metallic gold is put on in the 
form of an oxyd, and the steel lustre is produced by metal- 
lic platinum. 

24. GLUCINUM. 25. YTTRIUM. 26. ZIRCONIUM. 

27. THORIUM. 28. CERIUM. 29. LANTANUM. 

573. All these metals are so rare as to be known only to 
chemists. Their oxyds occur in several minerals, nearly all 
of which are among the most uncommon specimens in min- 
eralogical collections. Glucina, (24,) or the sesquioxyd of 
glucinum, (G 2 3 ,) is the most abundant, being found to the 
amount of 17 per cent, in the gems, beryl, emerald, and 
chrysoberyl. It very much resembles alumina, and is 
named in allusion to the sweet taste of its salts. Yttria, (25,) 
the oxyd of yttrium, (YO,) is a white earthy powder, form- 
ing sweetish salts, but differing from alumina and glucina in 
not being redissolved like them in an excess of potash and 
soda : this earth is found in the minerals yttro-cerite, gadoli- 
nite, and yttro-tantalite. Zirconia, (26,) sesquioxyd of zir- 
conium, (Zr 2 3 ,) which is the earth of the zircon or hyacinth, 
much resembles alumina, but differs from it and from gluci- 
cina, yttria, and thorina, by being precipitated from its 
solutions, as an insoluble sulphate, by boiling with solution 
of sulphate of potash. Thorina, (27,) the oxyd of thorium, 
is found in only one or two very rare minerals, as in thorite 
and monazite ; its specific gravity is 9, being much higher 
than any other earth. Cerium, (28,) and Lantanum, (29.) — 
The oxyds of these two rare metals are invariably associated 
with each other, and also with that of another metal, didy- 
mium, not yet fully described ; they are found only in some 
very rare minerals, as cerite, allanite, monazite, &c. The 
oxyd of cerium forms beautiful yellow salts, while the oxyd 
of lantanum forms equally beautiful rosy compounds ; the 
latter has been named in allusion to its having been long con- 
cealed or hidden under cerium, with which it is associated. 



572. How is porcelain colored ? 573. What six metals included 
in this section ? In what mineral is glucina found ? Describe yttria. 
In what mineral is zirconia found ? What are its properties ? What 
is said of thorium ? With what is cerium always associated ? 



3J2 METALLIC ELEMENTS. 

CLASS IV. METALS WHOSE OXYDS FORM POWERFUL 
BASES. 

30. MANGANESE. 

Equivalent, 27-67. Symbol, Mn. Density, 8. 

574. Manganese is never found as a metal in nature, but 
may be produced from its black oxyd by a high heat with 
charcoal. Metallic manganese is a gray brittle metal, not 
magnetic, and resembles some varieties of cast iron. It dis- 
solves rapidly in sulphuric acid with escape of hydrogen. 

Manganese in the form of the black oxyd is an important 
and pretty common metal. Its great use is for producing 
chlorine, (260,) and in the manufacture of glass, where it 
acts by its oxygen to decolorize the compound. 

575. The oxyds of manganese are numerous ; we give 
the formulas of six, and there are possibly one or two more, 
viz: protoxyd, MnO ; sesquioxyd, (or braunite,) Mn 2 3 ; 
peroxyd, or deutoxyd, (pyrosulite,) Mn0 2 ; red oxyd, (haus- 
mannite,) Mn 3 4 ; manganic acid, Mn0 3 ; hypermanganic 
acid, Mn 2 7 - 

The Protoxyd is a green -colored powder, formed from 
heating the carbonate of manganese in hydrogen. It is a 
powerful base, attracts oxygen from the air, and is the base 
of the beautiful rose-colored salts of manganese. 

The sesquioxyd or braunite occurs crystallized in octahe- 
drons, and forms belonging to the dimetric system. 

The Hydrated Sesquioxyd (manganite) is a finely crystal- 
lized mineral in long black prisms, found in superb speci- 
mens at Ilfeld, in the Hartz. In powder the sesquioxyd is 
brown ; it is decomposed by hydrochloric acid with the evo- 
lution of chlorine, but sulphuric acid combines with it to form 
a sesquisulphate, which yields a purple double salt with sul- 
phate of potash, (manganese alum,) isomorphous with the 
corresponding salt of alumina. This salt is, however, very 
easily decomposed by a gentle heat. 

574. What is said of manganese ? What form of it is most com- 
mon ? For what is it used ? 575. How many and what oxyds of 
manganese are named ? Which is the base of the rose-colored salts ? 
What is the sesquioxyd ? What is the hydrated sesquioxyd ? What 
is said of the sulphate of the sesquioxyd ? 



MANGANESE. 31 3 

576. The Peroxyd is the most common o» of manganese, 
and has a high commercial value. It is found abundantly at 
Bennington, Vt., and other places in this country. When 
crystallized it is called pyrolusite, and beautiful specimens of 
this mineral have been observed at Salisbury and Kent, Conn., 
among the iron ores. 

577. Manganic Acid is known only in combination, gen- 
erally as manganate of potash. This is best formed by mixing 
equal parts of finely powdered black oxyd of manganese and 
chlorate of potash with rather more than one part of hydrate 
of potash dissolved in a very little water. This mixture 
when evaporated is heated to a point short of redness, and a 
dark green mass is formed which contains manganate of potash. 
In this case the manganese obtains oxygen from the chlorate 
of potash, and the manganic acid thus formed combines with 
potash, giving a salt in green crystals. This salt, dissolved 
in water, gives a brilliant emerald-green solution, which 
almost immediately changes color, being in quick succession 
green, blue, purple, and finally crimson-red, and has thence 
been called chameleon mineral. This last color is due to 
the presence of permanganic acid, which, however, cannot 
be separated from its combinations, but forms a salt with 
potash in beautiful purple crystals. The compounds of per- 
manganic acid are more stable than the manganates. The 
salts of these acids are respectively isomorphous with sul- 
phates and perchlorates, (S0 3 and CI 2 7 .) 

578. The chlorids of manganese (MnCl and Mn 2 Cl 3 ) 
correspond to the protoxyd and sesquioxyd. The chlorid is 
formed abundantly in acting on black oxyd of manganese, 
(260,) with hydrochloric acid. The mixed solution of chlo- 
rids of iron and manganese is evaporated to dryness, and 
then heated to dull redness. The chlorid of manganese is 
then dissolved out from the dry mass, leaving the insoluble 
protoxyd of iron behind. It has a beautiful pink tint, and 
deposits tabular rose-colored crystals on evaporation. It is 
soluble in alcohol, and fusible by heat. The sesquichlorid 
is formed by solution of sesquioxyd in cold hydrochloric acid, 
but is decomposed by a gentle heat and evolves chlorine. 

576. Which is the most common ore of manganese ? Where and 
how is it found? 577. Describe manganic acid and the curious salt 
it forms with potash. What is the changeable compound called ? 
What is said of the salts of manganic and permanganic acid ? 578. 
Describe the chlorids of manganese. 
27 



314 



METALLIC ELEMENTS. 



579. The salts of manganese are numerous, and in a 
chemical view quite important. Sulphate of manganese is 
a very beautiful rose-colored salt, isomorphous with sulphate 
of magnesia. It is used to give a fine brown dye to cloth, 
being decomposed by a solution of bleaching-powder, which 
forms the brown peroxyd in the fibre of the stuffs. 



31. IRON. 

Equivalent, 27.14. Symbol, Fe. Density, 7*8. 

580. Iron is found malleable, and alloyed with nickel, in 
large masses of meteoric origin. One of these, discovered in 
Texas, weighs 1635 pounds, and is now in Yale College 
Cabinet. It is not certain that malleable iron of terrestrial 
origin has yet been discovered in nature. Iron is the most 
abundant and most important metal known to man. Its ores 
are found everywhere, and often in immediate connection 
with the coal and limestone necessary to reduce them to the 
metallic state. There is no soil, and scarcely any mineral, 
which does not contain some proportion of the oxyd of iron. 

581. Pure iron is difficult to prepare. The purest iron of 
commerce is always contaminated with a portion of silicon 
and carbon. When quite pure it is nearly white, quite soft, 

perfectly malleable, and the most 
tenacious of all metals. Its density 
is 7*8, which may be a little in- 
creased by hammering. It crystal- 
lizes in forms of the first class, as is 
beautifully shown in the crystalline 
structure of the meteoric iron. It fuses 
with extreme difficulty, first becom- 
ing soft or pasty, in which state it is 
welded. When intensely heated in 
air or oxygen gas it combines with 
oxygen, burning with brilliant light 
and numerous scintillations, and is 
converted into oxyd of iron, (255.) Iron also attracts oxy- 
gen at common temperatures, forming rust. This does not 




579. What is said in general of the salts of manganese ? 580. 
What is the equivalent of iron ? How is malleable iron found ? 
What is said of its abundance and value ? 581. Give the properties 
of iron. What is said of its fusion and welding? How does it be- 
have with oxygen ? 



IRON. 



315 



happen in dry air, but the presence of moistirre, and particu- 
larly of a little acid vapor, very much promotes its formation. 
Iron decomposes water very rapidly at a red heat, hydrogen 
being evolved. It is the chief medium of magnetism, being 
powerfully attracted by the magnet, and also itself suscepti- 
ble of this influence. 

582. The chief ores of iron are', (1,) brown hematite or 
hydrous peroxyd, from which the best iron is made. (2.) 
The red hematite and specular iron or peroxyd. (3.) Clay 
iron stone, which is an impure carbonate of iron, or carbon- 
ate of iron with carbonate of lime and magnesia. This is 
the nodular ore of the coal formations. (4.) Black or mag- 
netic oxyd of iron, which is the ore of the iron mountains 
of Missouri and of Sweden. 

583. The reduction of the ores of iron to the metallic 
state is performed in large furnaces called high or blastfur- 
naces. These are built of stone, 
in a conical form, 30 to 50 feet 
high, and lined internally with 
the most refractory fire-bricks. 
The furnace is divided into the 
throat, the fire-room, (&,) the 
boshes, (e,) (that portion sloping 
inward,) the crucible, (£,) and 
the hearth, (h.) The blast of 
air — supplied from very large 
blowing cylinders — is introduced 
by two or three tuyere pipes (aa) 
near the bottom. In the most 
improved furnaces, the air-blast 
is heated by causing it to pass 
through a series of pipes in the 
upper portion of the furnace, so 
as to have a temperature of 500° or more when it enters the 
furnace. When the furnace is brought into action, it is first 
heated with coal only, for about 24 hours ; and then is charged 
alternately with proper proportions of coal, roasted ore, and 
lime for flux, until it is quite full. When once brought into 
action, the blast is kept up for months or even years, until 




582. What ores of iron are enumerated ? 583. How is the reduc- 
tion of iron effected ? Describe the high furnace. What is the hot 
blast ? 



316 METALLIC ELEMENTS. 

the furnace requires repairing. The ore is reduced on the 
boshes, and in the upper part of the crucible, and the melted 
metal collects on the hearth, covered by the molten flux, 
which is a glass formed by the fusion of the lime used and the 
earthy parts of the ore. From time to time, the iron is 
drawn off by an opening previously stopped with clay, and 
run into rude open moulds in sand. This is cast iron, and 
is of various qualities, according the various character of the 
ore, and the working of the furnace. If malleable bar iron is 
wanted, the cast-iron is again melted, in what is called the 
puddling furnace, where it is stirred about by an iron rod, in. 
contact with oxyd of iron, and a current of heated carbonic! 
oxyd from the high furnace. It gradually becomes stiff and 
pasty from the burning out of the carbon, and from some 
molecular change not well understood. It is finally raised in 
a rude ball and placed under the blows of a huge tilt-hammer, 
when the scoria is pressed out and the particles made to 
cohere. It grows tenacious by a repetition of this process, 
being cut up and piled or faggoted and reheated several 
times, until it is finally made into tough and fibrous metal. 

584. Steel is formed from refined iron by heating in con- 
tact with charcoal in close vessels, (called cementation.) It 
gains from one to two per cent, of carbon, becomes fusible, 
and can be tempered according to the use for which it is 
designed. 

585. The oxyds of iron are four, viz : (1,) protoxyd, 
(FeO;) (2,) sesquioxyd, commonly called peroxyd, (F^Og ;) 
(3,) black oxyd, (magnetic oxyd,) (Fe^,) and (4) ferric acid, 
(FeO s .) 

(1.) The Protoxyd of Iron is a powerful base which is 
unknown in nature except in combination. It saturates 
acids completely and is isomorphous with a large class of 
bodies, of which zinc and magnesia are examples, (232.) 
This oxyd is thrown down from its solutions by potash, as a 
whitish bulky hydrate, that soon gains another dose of oxy- 
gen from the air becoming brown, and finally red. Its salts 
when soluble have a styptic taste like ink and a greenish 
color. 



What is the operation of the furnace ? What is cast iron ? How 
is malleable iron made from cast iron ? 584. What is steel ? 585. 
What are the oxyds of iron ? Give their formulas. Describe the 
protoxyd. 



IRON. 317 

586. (2.) The Peroxyd of Iron is found native in the 
beautiful specular iron of Elba, and also in the red and 
brown hematites. It is slightly acted on by the magnet, and 
after ignition is almost insoluble in strong acids. It is iso- 
morphous with alumina, and is generally associated with it in 
soils and many minerals. It is often of a brilliant red, and 
as ochre of various tints is much used as a pigment. Am- 
monia precipitates it from its solutions as a bulky red hydrate. 

587. (3.) Black Oxyd of Iron is familiarly known in the 
common magnetic iron ore and native lode-stone. It crystal- 
lizes in octahedrons. It forms no salts. The finery cinders 
or scales thrown off under the smith's hammer are this 
oxyd. 

(4.) Ferric Acid is a new compound, corresponding to 
manganic acid, discovered by M. Fremy. A ferrate of pot- 
ash is formed, when one part peroxyd of iron and four parts of 
nitre are heated to full redness in a covered crucible for an 
hour. The ferrate of potash is dissolved out of the porous 
mass by ice-cold water. The solution has a deep amethys- 
tine color, and is easily decomposed by heat. A soluble 
salt of baryta precipitates ferric acid as a beautiful red ferrate 
of baryta, which is permanent. 

The chlorids of iron (FeCl and Fe 2 Cl 3 ) correspond to the 
protoxyd and sesquioxyd (peroxyd) of the same base. The 
latter is often used in medicine and may be formed by satu- 
rating hydrochloric acid with freshly prepared peroxyd of 
iron. The protiodid of iron is also a valuable medicine. 

588. The sulphurets of iron are found native, and are 
well known as pyrites. The protosulphuret is easily formed 
artificially, by fusing sulphur with iron-filings ; they ignite 
with a vivid combustion, (459,) and protosulphuret of iron is 
formed, which is much used in preparing sulphureted hydro- 
gen. Yellow iron pyrites and white iron pyrites are 
dimorphous forms of the bisulphuret, (FeS 2 :) the first is one 
of the most common of crystallized minerals. The mag- 
netic sulphuret, magnetic pyrites, corresponds in composition 
to the magnetic oxyd. 



586. How is the peroxyd known ? 587. What is the black oxyd ? 
What is ferric acid ? What chlorids of iron are named ? What 
oxyds do they correspond to ? 588. What are the sulphurets of iron ] 
For what is the protosulphuret used ? What is the name of the 
ordinary sulphuret ? 
27* 



318 METALLIC ELEMENTS, 

589. Of the salts of iron, the green v itriol or protosul- 
phate (FeO, S0 3 + 7HO) is the most important. It is made 
in immense quantities, as at Stafford, Vt., from the decompo- 
sition of iron pyrites, which furnishes both the acid and the 
base. This salt crystallizes beautifully, and is much used as 
the basis of all black dyes and ink, and in the manufacture 
of prussian blue. It is called copperas in the arts. Persul- 
phate of iron is a sulphate of the peroxyd, (Fe 2 3 + 3S0 3 .) 
Carbonate of iron occurs in nature as spathic iron ore, 
which is isomorphous with carbonate of lime. A variety of 
steel is made directly from this ore without cementation, 
(584.) It is formed artificially by precipitating a solution of 
sulphate by an alkaline carbonate, and is used in medicine. 

The presence of a salt of iron is easily detected by the 
fine blue (prussian blue) formed on adding prussiate of 
potash to the solution ; an infusion of galls gives a black 
color (ink) to solutions of iron. 

32. CHROMIUM. 

Equivalent, 28*14. Symbol, Cr. Density, 6. 

590. Chromium in combination with iron is rather an 
abundant substance, particularly in this country, being found 
as chromic iron at Barehills, near Baltimore, Lancaster Co., 
Pa., and in other places. The beautiful red chromate of 
lead is also a natural product in Siberia. The metal, from 
its great affinity for oxygen, is very difficult to procure. It 
is a hard, almost infusible substance, resembling cast-iron, 
nearly insoluble in acids, and does not decompose water. It 
may be oxydized by fusion with nitre, but does not change 
in the air. 

591. Chromium forms five compounds with oxygen; of 
which the sesquioxyd (Cr 2 3 ) and chromic acid (Cr0 3 ) are 
the most important. Chromium bears the strongest analogy 
in its chemical character to manganese and iron. The per- 
fect identity of constitution in the oxyds of these three metals 
is shown in the following tabular arrangement : 



589. Which of the salts of iron are named as very important ? 
How and where is it made in this country ? What is the carbonate 
and for what used ? 590. Give the equivalent and symbol of chro- 
mium. How is it found associated? What of the metal? 591. 
What compounds does chromium form with oxygen ? 



CHROMIUM. 319 

Acids. 



Protoxyd. Sesquioxyd. Black oxyd. 



Manganese forms, MnO Mn20 3 Mn 3 04 Mn03 Mn 2 7 . 

Iron forms, FeO Fe 2 3 Fe 3 4 Fe0 3 

Chromium forms, CrO Cr20 3 Cr 3 4 Cr0 3 Cr 2 07. 

The Protoxyd of Chromium has only very lately been 
formed by M. Peligot, and is a strong base. It acts in com- 
bination like the protoxyd of iron, with which it is isomor- 
phous. 

592. The Sesquioxyd of Chromium is easily prepared, by 
treating a boiling and rather dilute solution of bichromate of 
potash, with an excess of hydrochloric acid, and then with 
small successive portions of alcohol or sugar, until it assumes 
a fine emerald green tint. Ammonia in slight excess will 
now throw down the hydrated oxyd as a bulky pale green 
precipitate, soluble in acids. When this precipitate is dried, 
it shrinks very much, and on ignition suddenly undergoes 
a vivid incandescence and becomes deep green. The sesqui- 
oxyd of chromium is a feeble base like those of iron and 
alumina, and may replace them in combination, as in the for- 
mation of chrome alum with sulphate of potash. All the 
salts of this oxyd are either emerald green or bluish purple. 
It imparts a rich tint of green to glass and porcelain, and is 
the cause of the color of the emerald. 

The Protochlorid of Chromium (CrCl) is obtained as a 
white and very soluble substance by 'the action of dry hydro- 
gen gas on the following compound. The Sesquichlorid (Cr 2 
Cl 3 ) is prepared by passing chlorine gas over an ignited mix- 
ture of the sesquioxyd and charcoal. It forms a crystalline 
sublimate of a peach-blossom color, and is insoluble in water. 
The sesquioxyd dissolves in hydrochloric acid, but the hydra- 
ted chlorid thus obtained is decomposed by heat. 

593. Chromic Acid (Cr0 3 ) is readily formed by treating 
a cold and concentrated solution of bichromate of potash with 
one and a half parts of sulphuric acid. The mixture when 
cold deposits brilliant ruby-red prisms of chromic acid. The 
sulphate of potash in solution above, may be turned off, and 
the chromic acid dried on a porous brick, being carefully 



With what metals is it closely allied ? How is this relation 
shown ? Give the comparative formulas of the oxyds of manganese, 
iron, and chromium. What is said of the protoxyd ? 592. How is 
the sesquioxyd prepared ? What are \ts properties and analogies I 
593. How is chromic acid prepared / What are its properties ? 



320 



METALLIC ELEMENTS. 



covered with a glass to prevent access of organic matters, 
which at once decompose it. If a little of this acid be 
thrown into alcohol or ether, the violence of the action is 
such as to set fire to the mixture. Chromic acid forms 
numerous salts, which are all highly colored. 

594. The Chr ornate of Potash and the Bichromate are 
both familiar examples. The first, (KO, Cr0 3 ) is formed 
on a very large scale by decomposing the native chromic 
iron with nitrate of potash, by aid of heat. Chromate of 
potash is dissolved out from the ignited mass, and crystal- 
lizes in anhydrous yellow crystals. It is isomorphous with 
sulphate of potash, dissolves in two parts of cold water, and 
is the source of all the preparations of chromium. 

Bichromate of Potash (KO, 2Cr0 3 ) is formed by adding 
sulphuric acid to a solution of the yellow chromate, when 
half the potash is removed, and the bichromate crystallizes 
by slow evaporation in brilliant red crystals of a rhombic form, 
which are soluble in ten parts of cold water. 

595. Chromate of Lead — Chrome Yellow — (PbO,Cr0 3 ,) 
is the well-known pigment prepared by precipitating the 
nitrate or acetate of lead by a solution of chromate or bichro- 
mate of potash. Chrome Green is the oxyd of chrome, pre- 
pared in a particular way. 

Chlorochromic Acid (Cr0 2 Cl) is a deep red volatile 
liquid resembling bromine, which appears when equal 
weights of common salt and bichromate of potash are 
intimately mixed, and heated in a retort with three parts of 
sulphuric acid. The chlorochromic acid distils over, filling 
the receiver with a superb ruby-red vapor. Water decom- 
poses it, forming chromic and hydrochloric acids. 

33. NICKEL. 

Equivalent, 29*59. Symbol, Ni. 

596. Nickel is rather a rare metal, but may be prepared 
from the speiss or crude nickel of commerce. It is white 
and malleable, having a density of 8*27, and fuses above 
3000°. It is not easily oxydized, and is one of the two or 



Describe the chlorids of chromium. 594. How is chromate of 
potash formed ? Bichromate of potash is how formed ? 595. What 
is chrome yellow ? What chrome green ? Describe chlorochromic 
acid. 596. In what state does nickel occur in nature ? 



COBALT. 321 

three magnetic metals ; magnets may be maae of it nearly 
as powerful as those of iron. Nickel is almost always found 
alloyed in masses of meteoric iron. In this country it has 
been obtained at Chatham, Ct. as an arseniuret, and also at 
Mine la Motte, in Missouri, as an earthy oxyd associated 
with cobalt. A beautiful green hydrous oxyd of nickel has 
been found lately in Lancaster Co., Pa., having the composi- 
tion NiO+2HO. 

There are two oxyds of nickel. The protoxyd (NiO) is 
prepared by precipitating a solution of nickel by caustic pot- 
ash, which gives a grass-green hydrated oxyd, which by 
heat loses its water and becomes gray. The oxyd of nickel 
is isomorphous with magnesia, and has been obtained crys- 
tallized in regular octahedrons. The salts of this oxyd have 
a fine green color, which they impart to their solutions. 

The peroxyd of nickel (Ni0 3 ) is a dull black powder, of 
no particular interest. 

597. The Sulphate of Nickel (NiO,S0 3 + 7HO) is a fine- 
ly crystallized salt occurring in green prisms, which lose their 
water of crystallization by heat. It forms beautiful well 
crystallized double salts, with the sulphates of potash and 
ammonia. Oxalic acid precipitates an insoluble oxalate of 
nickel from the solution of the sulphate, and the metallic 
nickel is easily obtained from the oxalate by heat. 

Nickel is chiefly employed in making German silver, a 
white malleable alloy, composed of copper 100, zinc 60, and 
nickel 40 parts. 

34. COBALT. 

Equivalent, 29*52. Symbol, Co. 

598. Cobalt is a metal almost always associated with 
nickel, and closely resembling it in many of its reactions. 
When pure it is a brittle reddish white metal, with a density 
of 8*53, and melts only at very high temperatures. It is 
generally said to be magnetic, but is not so when quite pure. 
It dissolves with difficulty in strong sulphuric acid, and is not 
oxydized in air. It forms two oxyds every way analogous 
to those of nickel. Its protoxyd is a grayish pink powder, 
very soluble in hydrochloric acid, and forming pink salts. 
This oxyd occurs native. 

Describe its properties. What are its oxyds ? In what form does 
the protoxyd crystallize ? 597. Describe the sulphate and oxalate 
of nickel. What is the composition of German silver ? 598. Wha* 
are the characters ©f cobalt ? 



322 METALLIC ELEMENTS. 

The Chlorid of Cobalt (CoCl) is formed by dissolving the 
oxyd in hydrochloric acid. The solution is pink, and when 
very dilute may be used as a blue sympathetic ink, which 
may be made green by mixing a little chlorid of nickel. 
Writing made with this on paper is colorless when cold, but 
becomes of a fine blue or green when gently warmed, and 
loses its color again on cooling. 

The salts of cobalt and nickel are isomorphous with those 
of magnesia. They are not thrown down by sulphureted 
hydrogen, but give blue or green precipitates with potash, 
soda, and their carbonates. The same precipitates with 
ammonia are soluble in excess of that reagent. Oxyd of 
cobalt imparts a splendid blue to glass, and the pulverized 
glass of this color is called smalt and powder blue. Zaffre 
is an impure oxyd of cobalt used to give the fine blue color 
to common earthen ware. 

35. zinc. 

Equivalent, 33. Symbol, Zn. Density, 6*86. 

599. Zinc is an important and rather common metal. It 
is not found native, but a peculiar red oxyd of zinc abounds 
at Sterling, New Jersey, and calamine or carbonate of 
zinc is found abundantly in many places. The ores of zinc 
are reduced by heat and charcoal, in large crucibles closed 
at top, but having an iron tube descending from near the top, 
through the bottom, and terminating in a vessel of water. 
The metal being volatile, rises and escapes by the tube into 
the water. This is called distillation by descent. 

600. Zinc is a bluish white metal, easily oxydized in the 
air, and crystallizes in broad foliated lamina?, well seen 
in the fracture of an ingot of the commercial article. It is 
called spelter in the arts, and is used chiefly to alloy copper 
in forming brass. Zinc is not a malleable metal, at ordinary 
temperatures, but at a temperature of between 250° and 300° 
it becomes quite malleable, and is then rolled into sheet 
zinc. At 400° it is again quite brittle, and may be granula- 



What interesting experiment is mentioned with the chlorid ? 
With what metal is the oxyd of cobalt and its salts isomorphous ? 
What use is made of the oxyd of cobalt ? 599. How is zinc reduced 
from its ores ? 600. What are its properties ? At what temperature 
is it malleable ? 



CADMIUM. 323 

ted by blows of the hammer ; at 773° it melts, and if air 
has access to it, it takes fire, and burns rapidly with a bril- 
liant whitish green flame, giving off flakes of white oxyd of 
zinc, sometimes called lana philosophica. It is completely 
volatile at a red heat. 

The Chlorid of Zinc, ZnCl, is a salt easily prepared when 
zinc is dissolved in hydrochloric acid, hydrogen being 
evolved. 

Sulphuret of Zinc, Blende, ZnS, occurs native in the 
forms of the first crystallographic class, and is colored yel- 
low, brown, and black. This is one of the ores of zinc 
(called black Jack) from which the metal is obtained. 

The oxyd (ZnO) is a white powder, insoluble in water, 
but easily dissolved in all acids, forming a series of salts, of 
which the most important is — 

Sulphate of Zinc, or White Vitriol, ZnO, S0 3 + 7HO. — 
This salt has the same form as the sulphate of magnesia, and 
looks extremely like it. It dissolves in 21 parts of cold 
water, and forms double salts with the sulphates of ammo- 
nia and potash. It is a powerful emetic. 

Sulphuret of ammonium throws down a characteristic 
white precipitate of sulphuret of zinc from its neutral solu- 
tions. 

36. CADMIUM. 

Equivalent, 55*74. Symbol, Cd. Density, 8*65. 

601. Cadmium is generally found associated with zinc, 
and is almost as volatile as mercury. It is quite malleable, 
white, and harder than tin. It fuses at 442°, and volatilizes 
at a temperature a little above this. It is not easily oxydiz- 
ed, and is but slightly soluble in hydrochloric or sulphuric 
acids. Nitric acid dissolves it with ease, forming a salt 
from which sulphureted hydrogen throws down a very char- 
acteristic orange-yellow sulphuret. This compound is also 
found native and crystallized, (greenocfcite.) 

Its oxyd (CdO) is a bronze powder, formed by igniting the 
nitrate or carbonate. 



Is it combustible ? Describe the sulphuret. What is said of the 
sulphate? 601. What are the properties of cadmium ? Describe 
its sulphuret. 



324 METALLIC ELEMENTS. 



37. LEAD. 



Equivalent, 103*56. Symbol, Pb. Density, 11*35. 

602. This useful and familiar metal occurs in boundless 
profusion in this country, chiefly as galena, or sulphuret of 
lead, from which the metal is easily obtained by smelting the 
ore with a limited amount of fuel, at a low heat. The car- 
bonate, phosphate, chromate, and arseniate, are also natural 
salts of lead much prized by the mineralogist. Lead is a 
bluish gray metal, very soft and ductile, but not very tena- 
cious ; it oxydizes in the air quite rapidly, forming a coat of 
oxyd, or carbonate, which protects it from further corrosion. 
Its density is 11*35, and it fuses at 612°; when melted it 
combines rapidly with oxygen from the air, forming either 
protoxyd, or red oxyd, according to the heat. 

Lead is slowly acted upon by soft or rain water, and in 
some cases by hard water ; so that it is unsafe to use water- 
pipes of lead, unless it has been proved by experiment that 
the particular water in question does not act on this metal. 
It is a deadly poison, at least in the form of carbonate, which 
is generally produced under these circumstances. 

Lead does not easily dissolve in dilute acids, except in 
nitric, with which it forms a soluble salt : strong sulphuric 
acid dissolves it when heated, forming a nearly insoluble 
sulphate of lead. 

There are three oxyds of lead, of which only the protoxyd 
has basic properties. 

603. Protoxyd of Lead ; Litharge, PbO. — This oxyd is 
a yellow powder, formed by slowly oxydizing lead, with 
heat. It is slightly soluble in water, and the solution is 
alkaline. It fuses easily, and then dissolves silica with great 
rapidity; hence its use in glazing pottery, (571,) and in the 
manufacture of glass, (535.) It forms a large class of 
definite salts, which have often a sweet taste, as is seen in 
the acetate or sugar of lead. The sesquioxyd has the 
formula Pb 2 3 , and is a reddish yellow insoluble powder. 

The Peroxyd, Pb0 2 , is prepared by acting on the red lead 

602. What is the chief ore of lead ? Describe the metal. How 
does water affect lead ? 603. Describe the protoxyd of lead. The 
other oxyds. What use is made of litharge ? 



LEAD. 325 

with nitric acid ; it is a puce-colored body which acts the 
part of an acid, with bases forming salts. 

604. Red Oxyd, or Red Lead, Pb 3 4 . — This is a com- 
mon pigment, and is formed when melted lead is exposed to 
a temperature of 600° or 700°. It is of variable constitution, 
according to the temperature at which it is prepared. Acted 
on by hydrochloric acid, it evolves chlorine, and with sul- 
phuric acid, oxygen is given off. It is preferred to litharge 
for glass making. 

The chlorid and iodid of lead possess no particular interest ; 
the latter crystallizes in beautiful yellow scales from its so- 
lution in hot water. The sulphuret of lead is the native 
galena already mentioned, and occurs in brilliant cleavable 
cubes. Sulphureted hydrogen throws down a black sulphu- 
ret from all soluble salts of lead, being the best test of its 
presence. 

605. Zinc precipitates it from its solutions by electrical 
action (248) in beautiful crystalline plates of s^r^ 
metallic lead, which assume a branching form, Jv^p^ 
often an inch or two in length, and hence called f \ 
the lead tree, or arbor satvrni, from the alche- £fzZggrJ 
mistic name of this metal. The acetate or nitrate ^ 
may be employed ; an ounce of the salt is dis- 
solved in two quarts of water, and a piece of 
clean zinc suspended in it by a thread ; the pre- 
cipitation is gradual, and occupies one or two 
days. The arrangement is seen in the annexed 
figure. 

606. Carbonate of Lead; White Lead; PbO,C0 2 .— 
This salt is found beautifully crystallized in nature, but is 
prepared artificially in very large quantities, for the purposes 
of a paint. This pigment is obtained by casting lead in very 
thin sheets, which are then rolled up into a loose scroll and 
placed in a pot over a small quantity of vinegar, and so 
arranged as not to project above the pot, nor touch the 
vinegar. Many thousands of these pots are arranged in 
successive layers over each other, with boards between, and 
the interstices filled with spent tan, or fermenting stable 
dung, which gives a gentle heat to the acid. After a time 
the lead is completely converted into an opake white crust 



605. How is metallic lead produced from its solution ? 606. How 
is the carbonate prepared, and for what is it used ? 
28 



326 METALLIC ELEMENTS. 

of carbonate. The theory of this process will be explained 
when we describe the acetates of lead, (organic chemistry.) 
White lead is now largely adulterated by sulphate of baryta, 
but the fraud may be easily detected by dissolving the car- 
bonate in an acid, when the sulphate of baryta will be left 
behind. Carbonate of lead is highly poisonous. 

! 38. URANIUM. 

607. This is a very rare substance, found only in pitch- 
blende, uranite, and a few other rare minerals. Its chemical 
history is, however, possessed of considerable interest. 
There are three oxyds of uranium, viz., U0 2 , U 2 3 , and 
U 4 5 . The metal is usually obtained as a dark powder, 
but can be condensed into a white malleable form. It forms 
beautiful yellow salts. The phosphate of uranium and cop- 
per (uranite) is one of the most beautiful of minerals. 

39. COPPER. 

Equivalent, 31*65. Symbol, Cu. Density, 8*895. 

608. Copper has been in familiar use since the times of 
Tubal Cain, and is one of the most important metals to the 
wants of society. It is often found in the metallic state. 
The metallic copper of Lake Superior is associated with na- 
tive silver, and small proportions of silver are also often alloy- 
ed with the copper. One mass from this region now at 
Washington, weighs over 3000 pounds. Its most usual ores 
are the red oxyd of copper and the copper pyrites, or sul- 
phuret of copper and iron. The blue and green malachites, 
or carbonates of copper, and several other salts of this metal, 
are also found in the mineral kingdom. Copper is very 
malleable, and is the only red metal except titanium. It 
fuses at 1996°, and has a density of 8*895, which may be in- 
creased to 8*95 by hammering. It does not change in dry 
air, but in moist air becomes covered with a green coat of 
carbonate. It is stiffened by hammering or rolling, and 
softened again by heating and quenching in water. It may 
be drawn into very fine wire, which is an excellent conduc- 
tor of heat and electricity, and is, much used in electro-mag- 
netism, and for the telegraphic conductors. 

Nitric acid is the proper solvent of copper, sulphuric and 

607. What is said of uranium ? 608. In what state does copper 
occur in nature ? Describe its properties. 



copper. 327 

hydrochloric acids scarcely acting upon it.*" It forms two 
oxyds, the protoxyd and the suboxyd. 

609. The first, or Black Oxyd of copper, CuO, is the 
base of all the blue and green salts of copper. It is formed 
by decomposing the nitrate with heat. It is black and very 
dense, quite soluble in acids, and forms many important salts 
which are isomorphous with those of magnesia. It yields 
all its oxygen to organic matters at a red heat, and for this 
purpose is much used in their analysis. 

The Suboxyd or Red Oxyd of Copper, Cu 2 O, is found na- 
tive in beautiful octahedral crystals, and is also formed when 
copper is oxydized by heat. This oxyd communicates to glass 
a magnificent ruby-red color. The chlorids and iodids of 
copper are of no great importance. 

610. Sulphate of Copper ; Blue Vitriol, CuO SO3 + 5HO, 
is an important salt, crystallizing in large beautiful blue 
rhombs, which are soluble in four parts of cold and two parts 
of hot water. It loses its water by a gentle heat and falls to 
a white powder. It is much used in dyeing, and for excit- 
ing galvanic batteries. With ammonia it forms a dark blue 
crystallizable compound. 

611. Nitrate of Copper, CuO, N0 5 + 3HO, is formed by 
dissolving copper in nitric acid to saturation, and is a deep 
blue crystallizable, deliquescent salt, very corrosive, and easily 
decomposed ; a paper moistened with a strong solution of 
this salt cannot be rapidly dried without taking fire, from the 
decomposition of nitric acid. 

Ammonia detects the smallest traces of this metal in 
solution, by the deep violet blue of the ammoniacal salt of 
copper which is formed. Iron precipitates it from its acid 
solutions as a brilliant red coating. 

CLASS V. METALS WHOSE OXYDS ARE WEAK BASES 
OR ACIDS. 

40. VANADIUM. 41. TUNGSTEN. 42. MOLYBDENUM. 
43. COLUMBIUM. 44. TITANIUM. 

612. The first five metals of this class are so rare that 
we shall dwell on them very briefly. 

609. What are the most important facts relative to the black oxyd 
of copper ? Describe the suboxyd. 610. Describe sulphate of 
copper. 611. What is the nitrate? How does it affect organic 
matter ? How is copper detected ? 612. Enumerate the five metals 
described in this section. 



328 METALLIC ELEMENTS. 

(40.) Vanadium is described as a very infusible, brittle, 
white metal, and dissolved only by aqua regia, affording a 
blue solution. It is found only in one or two very rare 
minerals, as in the vanadinite, or vanadiate of lead, acting 
the part of an acid. It appears to be closely allied to chro- 
mium. 

(41.) Tungsten, so named in allusion to its great weight, is 
found as tungstic acid in two or three rare minerals, viz. 
wolfram and tung state of lime. The native tungstic acid has 
also been observed at Monroe, Ct. Metallic tungsten re- 
sembles vanadium in physical characters, but it takes fire 
when heated in air in a state of division. It has a density 
of 17-4. 

There are two oxyds of tungsten : the first (W0 2 ) forms 
no salts ; the second, tungstic acid, (W0 3 ,) is a yellow 
powder, insoluble in water, but is easily dissolved in 
ammonia. 

(42.) Molybdenum. — Sulphuret of molybdenum is a rather 
common mineral, found in soft scales resembling graphite. 
The metal is obtained from its oxyd, and is very infusible, 
white and brittle, having a density of 8*6. 

It forms three oxyds, MO, M0 2 , M0 3 , of which the last 
only has much importance ; it resembles tungstic acid in 
being soluble in alkalies. It forms a beautiful yellow salt 
with lead, which is found native. The native sulphuret may 
be converted into impure molybdic acid by heat. 

(43.) Columbium, or Tantalum. — This metal was named 
after tl.is country by Mr. Hatchett, its discoverer, who found 
it among some ores sent to the Royal Society in London, by 
Gov. Winthrop, from Connecticut. 

Columbite (columbate of iron) is found at Haddam and 
Middletown, sometimes in large crystals. Professor Shepard 
procured the metal in a crucible lined with charcoal, as a 
dull, very infusible, brittle body, having a density of 5*7. 
Columbium forms two oxyds, T0 2 and T0 3 . The last is 
columbic acid, a white powder, soluble in acids, and forms 
almost insoluble salts with the alkalies and metallic oxyds. 
It is with this acid that the oxyds of the two new metals, 
pelopium and niobium, are associated. 

(40.) What is vanadium? Describe tungsten. (41.) What oxyds 
of tungsten are named ? (42.) How i3 molybdenum found ? What 
oxyd and what native salt of it are named ? (43.) Give the history 
of columbium. In what mineral is it found ? Describe its oxyds. 



tin. 329 

44. Titanium. — This metal is found crystgftlized in small 
brilliant cubes of a copper-red color in the slags of some iron 
furnaces. Its oxyd, beautifully crystallized, is well known 
to mineralogists, as rutile, anatase, and Brookite, three 
minerals specifically distinct, but chemically identical. 
Titaniferous iron ore is also an abundant mineral. 

Titanic Acid, Ti0 2 , is soluble in strong hydrochloric acid, 
but on dilution and boiling is all precipitated. It is a white 
insoluble powder, much resembling silica. It gives a peculiar 
tint to porcelain, and is used for this purpose in preparing 
artificial teeth. 



45. TIN. 

Equivalent, 58*82. Symbol, Sn, (Stannum.) Density, 7*29. 

613. Tin is one of those metals which have been known 
from the most remote antiquity. The mines of Cornwall 
have been worked for the oxyd of tin, since the times of the 
Greeks and Phoenicians. It has been found in this country 
only at Jackson, N. EL, in small quantities. Tin is a white 
metal with a brilliant lustre, not easily tarnished, and resist- 
ing the action of acids to a remarkable degree. It is soft, 
very ductile, laminable, and malleable. Tinfoil is made of 
one-thousandth of an inch in thickness, or even much thinner. 
A bar of tin when bent gives a peculiar crackling sound, from 
the disturbance of its crystalline structure, familiarly called 
the cry of tin. It is one of the best conductors of heat and 
electricity. 

614. Tin has a density of 7-29, and fuses at 442°. Its 
alloys are very valuble; gun-metal (copper 90, tin 10) is 
one of the strongest alloys known, of a reddish yellow ; bell- 
metal (copper 78, tin 22) is a very sonorous and brittle alloy, 
of a pale yellow ; and speculum metal (copper 70 to 75, and 
tin 25 to 30) is a brilliant, almost white, and excessively 
brittle alloy. Pewter is a mixture of tin and antimony or 
lead. Tin-plate is only sheet-iron coated with tin. 



(44.) How is titanium found V What minerals contain it ? 
Describe titanic acid. 613. What history is given of tin? What 
are its equivalent and general properties ? 614. Give its density and 
fusibility. What is said of its alloys with copper ? What is tin- 
plate ? and what pewter '! 

28* 



330 METALLIC ELEMENTS. 

Strong nitric acid does not dissolve tin, but the addition of 
a little water to the acid causes a violent action, and the tin 
is speedily oxydized. 

615. There are three oxyds of tin : the protoxyd, SnO ; 
the sesquioxyd, Sn 2 3 ; and the peroxyd, Sn0 2 . (1.) This 
is obtained by precipitating a solution of protochlorid of tin 
with an alkaline carbonate, which yields a bulky hydrate of 
the protoxyd. It is a very unstable compound, passing into 
the peroxyd at a very moderate heat. (2.) The sesquioxyd 
is a grayish powder, which has been but little examined. 
(3.) The peroxyd is found native in the beautiful crystallized 
tin stone. It may be obtained in a soluble, and an insoluble 
condition. When the perchlorid is precipitated by an alkali, 
the bulky white precipitate of hyd rated peroxyd which 
appears, is easily soluble in acids ; but if tin is acted on by 
an excess of moderately strong nitric acid, a white insoluble 
powder is formed, which is not acted on by the strongest 
acids. Heat converts both into a lemon-yellow powder, 
which dissolves in alkalies, but not in acids, and which is 
known as stannic acid ; it reddens test-paper, and forms 
salts. The putty used to polish stone and glass is the 
peroxyd of tin. 

616. Protochlorid of Tin, which is prepared by dissolving 
tin in hot hydrochloric acid, is a powerful deoxydizing agent, 
and reduces the salts of silver, mercury, platinum, &c, to 
the metallic state. The anhydrous protochlorid is formed 
by heating protochlorid of mercury with powdered tin. 

617. Perchlorid of Tin is a dense fuming liquid, long 
known as the fuming liquor of Labavius. It is formed by 
distilling a mixture of 1 part of powdered tin and 5 of 
corrosive sublimate. The tin mordant used by the dyers is 
formed by dissolving tin in hydrochloric acid, with a little 
nitric, at a low temperature, or by passing chlorine gas 
through the protochlorid. 

The sulphurets of tin correspond to the chlorids. The 
bisulphuret (aurum musivum) is used as a bronze color for 
imitating gold in ornamental painting and printing. 

How does strong nitric acid affect it ? 615. What oxyds of tin 
are there ? What is the protoxyd ? Describe the peroxyd. What 
two modifications of it are named ? How does heat affect them ? 
What is 'putty V 616. How is protochlorid of tin employed as a 
reagent ? 617. What is perchlorid of tin, and how prepared ? What 
is the tin mordant ? What sulphurets of tin are there ? 



BISMUTH. 331 

The alchemistic name for this metal was Jove, and the 
preparations of tin are still called Jovial preparations. 

46. BISMUTH. 

Equivalent, 70*95. Symbol, Bi. Density, 9*82. 

618. Bismuth is found native, and also in combination 
with other substances. Native bismuth is found at Monroe, 
Conn. It is a brittle, highly crystalline metal, of a red- 
dish white color, with a density of 9*82, and fuses at 497°. 
It is obtained in large and beautiful cubical crystals, by per- 
forating the crust of a mass which is just cooling from a state 
of fusion in a crucible, and pouring out the still fluid interior. 
The vessel will be lined with a multitude of brilliant crystals. 

It dissolves in nitric acid, but like other metals of this 
class, does not decompose water under any circumstances. 

619. Two oxyds of bismuth are known. The protoxyd 
(BiO) is formed by gently igniting the subnitrate, and is a 
yellowish powder, easily soluble in acids, and is the base of 
all the salts of bismuth. It is, however, a very feeble base, 
since even water decomposes its salts. The peroxyd (Bi 2 3 ) 
is not of much interest. 

620. The Nitrate of Bismuth (BiO,N0 5 + 3HO) is the 
most interesting of its salts. It may be obtained from a 
strong solution in large transparent crystals, which are 
decomposed by water. It is a striking and instructive 
experiment, to turn the solution of the nitrate of bismuth into 
a large quantity of water, when it is immediately decomposed, 
with the production of a copious white precipitate of subnitrate 
of bismuth. This is owing to the superior basic power of 
the water, which takes a part of the nitric acid. The white 
precipitate is a basic nitrate, (BiO,N0 5 + 3BiO,HO.) 

621. The alloy of bismuth known as Newton's fusible 
metal, is formed of 8 parts bismuth, 5 parts lead, and 3 parts 
tin, and melts below 212°. It is much used in taking casts 
of medals. The expansion of bismuth in cooling, renders it 
a valuable constituent of alloys, where sharpness of impression 
in casting is important. 

618. What is the color and fusibility of bismuth ? Describe its 
crystals, and the mode of obtaining them. 619. How many oxyds 
has this metal ? 620. What is the most interesting property of the 
nitrate ? 621. What is the composition of Newton's fusible metal ? 



332 METALLIC ELEMENTS. 



47. ANTIMONY. 

Equivalent, 129-04. Symbol, Sb, (Stibium.) Density, 6*7. 

622. This* metal is derived chiefly from its native sul- 
phuret, which is a rather abundant mineral. The metal is 
obtained by fusing the sulphuret with iron-filings, or car- 
bonate of potash, which combines with the sulphur and sets 
free the metal. It is a white brilliant metal with a blue tint, 
forming broad rhomboidal crystalline plates. It is very brit- 
tle, and like bismuth may be reduced to a fine powder. It 
fuses at about 1000°, or low redness, and at a higher heat 
is volatilized. It dissolves in hot hydrochloric acid, but nitric 
acid converts it into the insoluble white antimonic acid. 

Its alloy with lead is type-metal, which, like the alloys 
of bismuth, gives very sharp casts, by reason of the expan- 
sion from crystallization it suffers in solidifying, although it 
is remarkable that both of the constituent metals shrink when 
cast separately. Finely powdered antimony is inflamed in 
chlorine gas, forming the perchlorid. 

623. Three compounds of antimony and oxygen are 
known, viz : 

(1.) Oxyd of Antimony, Sb0 3 . — This oxyd may be ob- 
tained by digesting the precipitate from chlorid of antimony 
by water, with carbonate of potash or soda, or by burning 
antimony in a red-hot crucible. It is a fawn-colored insol- 
uble powder, anhydrous, and volatile when highly heated in a 
close vessel. Boiled with cream of tartar, (acid tartrate of 
potash,) it forms the well-known tartar emetic, which may 
be obtained in crystals from the solution. 

The Glass of Antimony is an impure fused oxyd, prepared 
for the purpose of making tartar emetic. Heated in air, this 
oxyd gains another equivalent of oxygen, and forms — 

624. (2.) Antimonious Acid, Sb0 4 . — This is a gray pow- 
der, not volatile, insoluble in acids, unless recently precip- 
itated. Its hydrate reddens litmus paper, and combines 
with alkalies. 

(3.) Antimonic Acid, Sb0 5 , is formed as already stated, 



622. How is antimony obtained ? What are its properties ? 623. 
How many compounds does antimony form with oxygen ? 624. De- 
scribe the two acids of antimony. 



ANTIMONY. 333 

when antimony is digested in an excess of Strong nitric acid. 
It dissolves in alkalies, with which it forms definite salts, 
that are again decomposed by acids, hydrate of antimonic 
acid being thrown down. The hydrate loses its water be- 
low a red heat, becoming a crystalline fawn-colored powder, 
and by a higher heat one equivalent of oxygen is expelled, 
antimonious acid being formed. 

625. There are chlorids and sulphurets of antimony, cor- 
responding to the oxyd and to antimonic acid. 

The Ter chlorid, Butter of Antimony, SbCl 3 , is made by 
distilling the residue of the solution of sulphuret of antimony 
in strong hydrochloric acid. When a drop of the distilled 
liquid forms a copious white precipitate on falling into water,! 
the receiver is changed, and the pure chlorid is collected. 
It is a highly corrosive fuming fluid, and by cooling forms a 
crystalline deliquescent solid. It is used in medicine as a 
caustic. Water decomposes it, but it dissolves in hydro- 
chloric acid unchanged ; water poured into the solution 
throws down a bulky precipitate which, is a mixture of oxyd 
and chlorid of antimony, and has long been known by the 
name of powder of algaroth. 

The bromid of antimony is a crystalline volatile com- 
pound. 

626. The Ter sulphuret of Antimony, SbS 3 , constitutes the 
common commercial sulphuret, and the beautiful crystallized 
native mineral. 

The Pentasulphuret of Antimony, SbS 5 , is formed by boil- 
ing the tersulphuret with potash and sulphur, and throwing 
down the compound in question by an acid, as a golden yel- 
low sulphuret, known by the name of sulphur auratum, 
or golden sulphur of antimony. More generally, how- 
ever, the decomposition on adding an acid, as above, gives 
us the oxy sulphuret of antimony, (SbS 3 + Sb0 3 ) which is 
a characteristic reddish-orange precipitate. This is the sub- 
stance known as kermes mineral, and is an article of the 
older medical practice. The solution of sulphuret of anti- 
mony in caustic potash and sulphur, is a case in which sul- 
phuret of potassium is a sulphur base, and sulphuret of anti 
mony, a sulphur acid. 



625. Describe the terchlorid and its decomposition. 626. What 
is said of the chlorids and sulphurets ? What is kermes mineral? 



334 METALLIC ELEMENTS. 

48. ARSENIC. 

Equivalent, 75-21. Symbol, As. Density, 5*884. 

627. Metallic Arsenic is found native in thick crusts, 
called testaceous arsenic, evidently deposited by sublimation. 
It is however more usually obtained from roasting the ores 
of cobalt, nickel, and iron, with which metals it is often 
combined, forming arseniurets. The vapors of arsenious 
acid given out in the roasting, are condensed in a long hori- 
zontal chimney, or in a dome constructed for the purpose ; 
the first product being purified by a second sublimation. 
Arsenic is a brilliant steel-gray metal, brittle, and easily 
crystallized. It cannot be sublimed unchanged in presence 
of air, but may be so in close vessels, at a temperature of 
356°, without previously melting. Its vapor has a very 
powerful garlic-like odor, like phosphorus. This metal is 
known by druggists under the absurd name of cobalt, and is 
sold in powder to destroy flies. Metallic arsenic is easily 
obtained by subliming the common white arsenic with black 
flux, (489,) in a vessel of hard glass, like a cologne vial or 
oil bottle. The metal forms a brilliant black crust in the 
upper and cooler parts of the vessel. 

Arsenic forms two compounds with oxygen. 

628. Arsenious Acid — White Arsenic — Rafs Bane, 
As0 3 . — This well known and fearful poison is formed as 
just stated, when metallic arsenic is sublimed in air, or when 
any of the ores of arsenic are roasted. This acid is what is 
usually known as arsenic in commerce. When newly 
sublimed, it is a hard transparent glass, brittle, and with a 
density of 3*7. It slowly changes to a white opake enamel. 
As sold in commerce, it is usually reduced to a white 
powder, rarely found without adulteration. It sublimes at 
380°, without change, and crystallizes in brilliant octa- 
hedrons, as may be well seen by heating a small quantity in 
a glass. tube. Its vapor is inodorous, but if sublimed from 
charcoal it gives the peculiar garlic odor of metallic arsenic, 
being reduced to that state. It is soluble in about 10 parts 
of hot water, and is almost tasteless, with a faint sweetish 



627. How is arsenic obtained, and what are its properties ? 628 
Describe arsenious acid. 






ARSENIC. 335 

flavor, which renders it the more dangerous poison, since no 
warning is given to the victim who takes it, as in case of 
most other metallic poisons. The solution in water is acid 
to test-paper, and deposits nearly all its arsenic in crystals, 
on cooling. H3»drochloric acid dissolves it, as also do 
alkalies, which however do not form crystallizable salts 
with it. The best antidote to the poisonous effects of arsenic 
is the hydrated peroxyd of iron, freshly precipitated, and used 
in its gelatinous condition. 

629. Arsenic Acid, As0 5 . — This acid is formed by 
adding nitric acid to the solution of white arsenic, in hydro- 
chloric acid, as long as any red vapors of nitrous acid show 
themselves, and then carefully evaporating the solution to 
entire dryness ; a white porous subcrystalline mass remains, 
which is slowly soluble in water. Its solution is a powerful 
acid, quite similar in chemical characters to phosphoric acid. 
The analogy is so great that there is a complete similarity in 
constitution, and even in external appearance, between all the 
salts of these two acids. For every tribasic phosphate we 
have an arseniate, not only similar in constitution, but iso- 
morphous, and so resembling it in all its external properties 
as not to be distinguished by the eye. Thus the tribasic 
phosphate of soda, (528,) and the tribasic arseniate of soda, 
are — 

Phosphate of soda, P0 5; 2 NaOHO 4- 24Aq. 

Arseniate of soda, As6 5 ,2NaOHO + 24 Aq. 

These, and many other facts, lead to the opinion that the 
elements are themselves isomorphous, and in fact arsenic has 
no claim to the metallic character but its lustre, being in 
chemical properties and natural affinities associated with 
phosphorus. 

630. The Chlorid of Arsenic (AsCl 3 ) is a fuming volatile 
liquid, decomposed by water, and very poisonous. The 
bromid and iodid are both crystallizable solids, also decom- 
posed by water. 

The sulphurets of arsenic are natural compounds, used 
as pigments, and also in pyrotechny. The first, AS 2 , is a 
red transparent body called realgar, and AsS 3 is the golden 
yellow orpiment. Both these substances are found native, 



629. How is arsenic acid obtained ? To what other acid is it 
allied, and how ? What is the real character of arsenic ? 630. 
Describe the sulphurets. 



336 METALLIC ELEMENTS. 

and as usually associated, they are brought from Koordistan 
in Persia, and from China. The higher sulphurets may be 
formed, which are As0 5 and As0 9 ; the former is the product 
thrown down by sulphureted hydrogen in a solution of arse- 
nic. All but the highest of these compoundsgare sulphur acids. 

631. Arseniureted Hydrogen. — This is perhaps the most 
deadly poison known. It is a gas produced by the action 
of dilute sulphuric acid on an alloy of zinc and arsenic, or 
by the evolution of hydrogen in presence of arsenic or 
arsenious acid. This gas is readily absorbed by a solution 
of sulphate of copper, and precipitates an arseniuret of that 
metal. It burns with a peculiar blue flame, and deposits 
metallic arsenic or arsenious acid. Marsh's test for arsenic 
depends on the generation of this gas. 

632. Detection of Arsenic as a Poison. — The fearful use 
which is made of this terrible poison in destroying human 
life, renders it of the first moment that we should know easy 
and certain process for its detection. Accordingly we find 
that very numerous methods have been proposed for this 
purpose, a few of which we will briefly mention. When a 
fluid, or other substance free from organic matter, is to be 
examined for arsenic, there are many tests which we can 
apply. (1.) Sulphureted hydrogen throws down the yellow 
sulphuret in acidulated solutions of arsenious acid ; this is 
redissolved by ammonia, and again precipitated by acids. (2.) 
Nitrate of silver produces a yellow precipitate of arsenite 
of silver in solutions of arsenious acid, if a trace of ammo- 
nia is present ; but the precipitate does not appear in an acid 
solution, and an excess of ammonia dissolves it. (3.) Sul- 
phate of copper gives a brilliant green precipitate of arsenite 
of copper, (ScheeWs green,) in alkaline solutions of arse- 
nious acid, which precipitate is redissolved by ammonia in 
excess. (4.) A clean slip of metallic copper placed in a 
solution of arsenious acid, is soon coated with a gray deposit 
of metallic arsenic ; this is known as ReinscK's test. 

633. All these tests taken collectively, constitute to the 
mind of the chemist a perfect demonstration of the presence 
of arsenic ; but they are liable to many objections arising 
from the presence of organic matters, of impurity in reagents, 



631. What are the characters of arseniureted hydrogen ? 632. 
What are some of the means of detecting the presence of this 
poison ? 






ARSENIC. 



337 



and from the possible presence of other metallic matters, as 
antimony, which forms a brick-red or yellowish sulphuret, 
and cadmium, whose sulphuret much resembles orpiment. 
It is therefore always demanded in judicial investigations, 
that no proof of the presence of arsenic shall avail except 
that of sublimed metallic arsenic. 

634. Reduction of Arsenic. — When it is possible to obtain 
from the suspected substance any grains of arsenious acid, 
these are carefully selected for the purpose of examination. 
If not, the yellow sulphuret obtained from the suspected 
solution by sulphureted hydrogen is employed, to produce 
the metallic arsenic. Either of these substances is introduced 
into a small tube of hard glass, drawn out at the lower part 
as here represented, and the narrow part of the 
tube is then filled with black flux to the shoulder, (a.) 
Its interior being wiped out, the flame of a small 
spirit-lamp is applied to the upper part of the mixture 
to expel any moisture it may contain, which is next 
carefully removed by bibulous paper. The flux is 
then gradually heated to redness from a to b, and 
the heat slowly carried down below b, until the 
lower part of the tube is fully red. If any arsenic 
is present it is sublimed, and deposited in a brilliant 
ring just above the shoulder, as seen in the figure. 
For further proof, the tube may be drawn off at a 
in the lamp-flame, and the metallic arsenic vola- 
tilized by the heat until it is all converted into 
arsenious acid, which a magnifier shows to be in 
brilliant white octahedral crystals. 

635. But the most common and most difficult case of 
testing for arsenic is when the fluids of the stomach, ejected 
by the patient, or the stomach itself and its contents, are to 
be examined. The organic matters present in all such 
cases, render the liquid tests quite worthless, and oblige us to 
have recourse to a method of which a brief sketch only can 
be presented. The suspected fluid, and the solid parts cut 
small, are placed in a large porcelain capsule with a con- 
siderable quantity of pure hydrochloric acid, and as much 
water as will make the mixture thin. This mixture is 



633. What other bodies resemble it in its reactions ? 634. How 
are we to obtain it in a metallic state ? 635. How do we ascertain 
its presence when mixed with organic matters ? 
29 



338 METALLIC ELEMENTS. 

heated on a water-bath, and while hot, small portions of 20 
or 30 grains of chlorate of potash are added to the mixture, 
at short intervals. The chlorine evolved by this treatment 
completely decomposes the organic matters, and the final 
result is the production of a yellow transparent fluid, which 
can easily be filtered. From this, sulphureted hydrogen in 
•excess will throw down all arsenic, antimony, &c, which 
may be present ; and after resolution and reprecipitation, the 
suspected sulphuret of arsenic may be reduced in the same 
way as has been just described. Another mode of reduction, 
however, is much to be preferred, where cyanid of potassium 
is employed in the reduction tube, in place of the black 
flux, with about three parts dry carbonate of soda, and the 
sulphuret. 

636. Marsh's test is one which is very convenient, sim- 
ple, and if used with care, satisfactory in most cases. It 

depends on the formation of arseniureted hy- 
drogen. The suspected substance is placed in 
a flask with the materials to generate hydrogen, 
(376.) This gas, as it issues from a jet, is set 
on fire, and if arsenic is present in the mix- 
ture, the flame burns with a peculiar blue 
light, and a clean plate of mica or porcelain 
held over it, is at once blackened by a film 
of metallic arsenic. The annexed figure 
shows a convenient form of this apparatus. 
The materials for hydrogen and the suspected 
body are put in the lower bulb, and dilute sul- 
phuric acid being turned into the upper bulb, 
hydrogen gas is generated, and may be delivered at will by 
the stop-cock and jet. Extremely minute traces of arsenic 
may be detected by this test. Antimony presents a some- 
what similar spot, but may easily be distinguished from arse- 
nic by a practised eye. It must be observed that all the 
reagents employed in this apparatus, the zinc, the acid, and 
even the glass of the vessel, may contain arsenic. 

49. OSMIUM. 

637. Osmium (Os, 99*56) is one of the rare metals 
which are associated with platinum. It has a density of 10-, 

636. Describe Marsh's test. What objections are there to his 
method ? 637. With what body is osmium associated ? 




MERCURY. 339 

and is of a white-bluish color, neither fusible^ nor volatile, but 
takes fire in the air, forming osmic acid, (Os0 4 ,) which is 
volatile and poisonous. Osmium forms four oxyds, viz : 
OsO, OS2O3, Os0 2 , and Os0 4 . Osmiate of potash is formed 
when the metal is fused with nitre. Osmium combines with 
sulphur and phosphorus, and has the same number of sulphu- 
rets as of oxyds and chlorids. 



CLASS VI. NOBLE METALS, WHOSE OXYDS ARE RE- 
DUCED BY HEAT ALONE. 

50. MERCURY. 

Equivalent, 101-26. Symbol, Hg, (Hydrargyrum.) Den- 
sity, 13*5. 

638. This is the only metal which is fluid at ordinary 
temperatures. It is found as native or running mercury in 
Spain and Carniola, and also as cinnabar or sulphuret of mer- 
cury, but it is a rather rare and costly metal. It has never 
been found in this country. The alchemists supposed it to 
be silver enchanted, (quick-silver,) and made many efforts to 
obtain from it the solid silver it was supposed to contain. 

Pure mercury is a silver- white, fluid metal, unchanged by 
air, and very brilliant. Cooled below — 40°, as when frozen 
by carbonic acid, (137,) it solidifies, and is then as malle- 
able as lead. It crystallizes at this degree of cold in cubes. 
It boils at 660°, and forms a colorless, very dense vapor. 
Even at 60°, a very rare vapor of metallic mercury (129) 
rises from it. If heated in the air at above 600°, it slowly 
passes to the condition of red oxyd of mercury, which is its 
highest combination with oxygen. 

639. The uses of mercury are numerous and important 
in the arts, and also in medicine. It forms alloys (amal- 
gams) with many other metals ; with tin it constitutes the 
brilliant coating of glass mirrors, (called silvering,) and it is 
of indispensable importance in procuring gold and silver 
from their ores. Its use in filling thermometers and baro- 
meters (76) has already been described. 

What are its properties ? What oxyds does it form ? What is 
the sixth class of metals ? 638. How is mereury found in nature ? 
What are its properties ? 639. What are the uses of this metal ? 



34-0 METALLIC ELEMENTS. 

Nitric acid dissolves mercury very rapidly even in the 
cold; hydrochloric acid scarcely acts on it, and sulphuric 
only by the aid of heat, when it forms an insoluble sul- 
phate of mercury, evolving sulphurous acid, (286.) The 
equivalent of mercury is often stated at 202*52, on the sup- 
position that the gray oxyd is the protoxyd ; but this seems 
to be more properly considered as a suboxyd, and the real 
protoxyd as the red oxyd. On this view the equivalent is 
stated at 101-26. 

Mercury may be so finely divided as to lose its metallic 
appearance entirely ; as in blue pill, mercurialized chalk, I 
(creta cum hydrargyro,) and mercurial ointment, which do I 
not, as has sometimes been stated, contain the suboxyd of 
mercury, but only mercury in a state of very minute mechan- 
ical division. 

640. The Gray, or Suboxyd of Mercury, Hg 2 0, is formed 
by digesting calomel in caustic potash, or by adding the 
same reagent to a solution of the nitrate of the suboxyd of 
mercury. It is an insoluble, dark gray powder, which is 
easily decomposed into metallic mercury and the red oxyd. 

The Red Oxyd, or Protoxyd, Red Precipitate, HgO, is 
prepared in the large way by, heatingNthe nitrate very cau- 
tiously, until it is quite decomposed, and a brilliant red crys- 
talline powder is left. It may also be formed by heating 
metallic mercury for a long time in a glass vessel nearly 
closed, and in this form is the preparation to which the old 
name of red precipitate per se was applied. Heat decom- 
poses this oxyd into oxygen and metallic mercury. It is, 
like the oxyd of lead, slightly soluble in water, and gives 
to it an alkaline reaction. It is a dangerous corrosive 
poison. 

641. The chlorids of mercury correspond to the oxyds, 
and are both very important compounds. 

(1.) The Subchlorid of Mercury, (Calomel,) Hg 2 Cl, is a 
well known medicine, and is easily formed by precipitating a 
solution of subnitrate with common salt. A white, insolu- 
ble, tasteless powder falls, which is the calomel. Even strong 
acids when cold do not affect it ; but it is instantly de- 
composed by alkalies and the suboxyd produced. Heat 



How do acids act upon it ? 640. How many oxyds does mercury 
form ? Describe the preparation of the red oxyd ? 641. How many 
chlorids are there ? How is calomel prepared ? 



MERCURY. 341 

sublimes it unchanged. Its complete insolubility at once 
distinguishes this safe and mild substance from the highly 
poisonous — 

(2.) Corrosive Sublimate, or Chlorid of Mercury, HgCl. 
— This salt is most economically prepared by the double de- 
composition of sulphate of mercury, by common salt, which 
by simple interchange gives corrosive sublimate and sulphate 
of soda, (HgO, S0 3 + NaCl = HgCl + NaO,S0 3 .) The chlo- 
rid is also formed by dissolving the red precipitate in hot 
chlorohydric acid. Corrosive Sublimate is a very heavy- 
crystalline body, soluble in about 15 parts of cold water, and 
in two or three parts of hot, giving a solution which pos- 
sesses the most distressing and nauseous metallic taste, 
and is a deadly poison. It is soluble in alcohol and ether. 
It melts and sublimes a little below 600°. Albumen com- 
pletely precipitates it, and the whites of eggs are therefore 
an antidote for this poison. For the same reason it is, 
doubtless, that timber and animal substances are preserved 
from decay, as in the Jcyanizing process, by steeping in solu- 
tion of corrosive sublimate. The albuminous portions of 
wood suffer decay sooner than the vegetable fibre, and these 
are rendered completely indestructible in the process of Mr. 
Kyan, which is now in use in our national ship-yards. 

642. There are two iodids of mercury, Hg 2 I and Hgl. — 
The second is a brilliant scarlet-red precipitate, formed 
by adding solution of iodid of potassium or hydriodic acid 
to a solution of corrosive sublimate. The iodid is at first yel- 
low, but soon passes by a molecular change into the splendid 
scarlet crystalline powder before noticed. It cannot be used 
as a pigment on account of its instability. 

643. Two sulphurets of mercury, Hg 2 S and HgS, exist, 
the first of which is formed when sulphureted hydrogen is 
passed through a solution of subnitrate of mercury, and is a 
black powder. The sulphuret, HgS, or cinnabar, is formed 
when the nitrate of mercury (nitrate of the red oxyd) 
is treated with sulphureted hydrogen. It is a black precipi- 
tate, but turns red when sublimed, and forms the familiar 



What is the process for obtaining corrosive sublimate ? How does 
it differ from calomel ? Describe the antidote for this poison and its 
effect upon it. What uses are made of chlorid of mercury ? 
642. Describe the iodid of mercury. 643. How many sulphurets 
of mercury are there ? 

29* 



342 METALLIC ELEMENTS. 

pigment ver 'million. This is the common ore of the quick 
silver mines. 

644. The nitrates of mercury. — The action of nitric 
acid on mercury varies with the temperature and the strength 
of the acid. In the cold, dilute nitric acid dissolves mer- 
cury, forming a neutral nitrate of the suboxyd ; but if the 
mercury is in excess, a salt is deposited in large and trans- 
parent white crystals, which is a nitrate with excess of base. 
If hot and strong, the nitrate of the red oxyd is formed, 
which is a very soluble salt not c.rystallizable. A basic salt 
of this oxyd may also be formed, which is decomposed by 
water. 

645. Sulphate of Mercury (HgO S0 3 ) results as an in- 
soluble, white, subcrystalline powder, by the action of the 
strong acid on metallic mercury, (286,) sulphurous acid being 
evolved. Boiling water decomposes this salt, removing a 
part of its acid, by which a yellow basic sulphate is formed, 
known as turpeth mineral. Its composition is 3HgO, S0 3 . 
The sulphate of the gray oxyd, Hg 2 0, S0 3 , is formed as a 
crystalline white powder by treating a solution of subnitrate 
of mercury with sulphuric acid. It is slightly soluble in 
water. 

646. Ammonia produces many interesting compounds 
with the salts of mercury, of which the white precipitate, as 
it is called, is best known. This falls when chlorid of mer- 
cury in solution is treated with ammonia in excess, and is 
considered as a double amide and chlorid of mercury, HgCl 
and HgNH 2 . 

All the compounds of mercury are volatile at a red heat, 
and those which are soluble, whiten a slip of clean copper by 
depositing metallic mercury on its surface. 

51. SILVER. 

Equivalent, 108-12. Symbol, Ag, (Argentum.) Density, 10'5. 

647. The mines of Mexico and the Southern Andes 
furnish most of the silver of commerce, although many 
mines of this metal are found in Spain, Saxony, and the 

What is vermillion ? 644. How are the nitrates of mercury ob- 
tained ? What is the nature of the nitrate of the red oxyd ? 645. 
How is the sulphate formed ? 646. What is the nature sf white pre- 
cipitate ? What are the characteristics of mercurial compounds ? 
647. From what sources is silver obtained ? 



SILVER. 343 

Hartz mountains. Galena, or the native suTphuret of lead, 
is also a constant source of silver, as it is rarely quite free 
from this precious metal. Silver is often found native, and 
also in combination with sulphur. 

The brilliant lustre and white color of this valuable metal 
are familiar to all. It is perfectly ductile and malleable, and 
in hardness stands between gold and copper. For the pur- 
poses of economy and in coinage it is essential to alloy it 
with about y L- part of copper, to render it sufficiently stiff and 
hard. 

Pure silver melts at 1873°, and when melted absorbs sev- 
eral times its volume of oxygen gas, which it parts with 
again on cooling. This renders silver a difficult metal to 
cast, and occasions the little projections and roughness usu- 
ally seen on silver which has been melted. 

Silver is obtained pure from its solution in nitric acid by 
precipitation with metallic copper, as a finely divided crystal- 
line powder ; or by decomposing its chlorid by fusion with 
two parts of dry carbonate of potash. Nitric acid dissolves 
silver in the cold with great rapidity, and if it contains any 
gold, this is left undissolved as a brown powder. 

Hydrochloric acid scarcely acts on silver, and sulphuric 
acid only when hot, forming the sulphate of silver, which is 
sparingly soluble in water. 

648. Silver is parted from galena, by a process called 
cupellation, or fusing at a white heat the pulverized galena 
and a certain quantity of metallic lead, on a little thick cup 
or cupel of bone-ashes, in a muffle exposed to a current of 
air. The lead oxydizes and is absorbed, while the silver is 
left in a brilliant metallic button on the cupel. In the large 
way this process is much facilitated by- the fact that the alloy 
of silver and lead is more fusible than pure lead, and the 
latter on cooling separates from the former, which may be 
drawn off, and contains all the silver. This small portion is 
cupelled, while the great bulk of the lead is returned to the 
arts uninjured. 

649. Three oxyds of silver are known by chemists ; the 
suboxyd, Ag 2 O ; the protoxyd, AgO ; and the peroxyd, 
Ag0 2 . We will now notice only the protoxyd. This is 
formed when the solution of silver in - nitric acid is saturated 

What are the characteristics of pure silver ? 648. How is it sepa- 
rated from lead ? 649. Describe the preparation and character of 
oxyd of silver. 



344 METALLIC ELEMENTS. 

with caustic potash, or when the chlorid of silver recently 
precipitated is digested in a solution of caustic potash of den- 
sity 1*3. It is a dark brown or black powder, if prepared 
by the first mode, or quite black and dense by the second 
process. It is a base forming well defined salts. Ammonia 
dissolves it readily, and it is also somewhat soluble in water, 
to which it gives an alkaline reaction. It is easily reduced 
by heat alone. Its solutions are at once detected by the 
bulky white curdy precipitate which they form with hydro- 
chloric acid or with common salt. This white precipitate 
turns dark by exposure to light. 

650. Chlorid of Silver, AgCl, is formed, as just remarked, 
when any soluble salt of silver is treated with a soluble 
chlorid or with hydrochloric acid. This substance fuses at 
a moderate red heat into a transparent pale yellow fluid, 
which is horny and tough when solid, and hence called 
horn silver, a form in which this metal is sometimes found in 
mines. It is easily reduced to the metallic state by the 
nascent hydrogen generated when zinc is acted on by dilute 
sulphuric acid in contact with the chlorid. Pure silver and 
chlorid of zinc result ; or, it may be reduced by fusion with 
twice its weight of carbonate of soda or potash. 

The iodid and bromid of silver are, like the chlorid, insolu- 
ble in water, and very sensitive to light. The Daguerreotype 
and calotype (62) are both dependent on the sensitiveness 
of these compounds to light, for the accuracy and beauty of 
their results. 

The sulphurets of silver are found native, and the tarnish 
which blackens silver articles on long exposure, is formed by 
sulphureted hydrogen in the air. 

651. The Nitrate of Silver, AgO, N0 5 , is a salt which 
crystallizes in beautiful flattened tables of a hexagonal form, 
which dissolve in half their weight of hot water. By heat 
it fuses, and when cast in cylindrical moulds forms the 
slender sticks called lunar caustic, so much used by the sur- 
geon. Its solution has a disgusting metallic taste even when 
very dilute, and is a most delicate test of the presence of 
chlorine or any of its compounds. It blackens rapidly in 



650. Describe the chlorid. How can it be reduced ? What are 
the relations of the silver compounds to light ? What is the action of 
sulphureted hydrogen on silver? 651. Describe the nitrate. What 
are its reactions ? 



GOLD. 345 

contact with organic matter when exposed to^the light, and 
forms an indelible ink, which is much used in marking 
linen. Solution of cyanid of potassium will remove the 
stain produced by nitrate of silver. Metallic copper at 
once throws down metallic silver from the nitrate, and solu- 
tion of nitrate of copper is formed. Mercury precipitates 
metallic silver from a dilute solution, in beautiful tree-like 
forms, called arbor Diana. Ammonia, by acting on pre- 
cipitated oxyd of silver, forms a fulminating compound. It 
is extremely hazardous to deal with, as it explodes even 
when wet. 

52. GOLD. 

Equivalent, 99.44. Symbol, Au. Density, 19*26. 

652. This valuable metal is found only in the metallic or 
native state, being very widely diffused in small quantities in 
the older rocks. From these, by the action of various 
causes, it finds its way into the sand of rivers, and is dis- 
tributed in small quantities, in many wide-spread deposits of 
coarse gravel or shingle, — as on the eastern flanks of the 
Ural Mountains, and over a wide belt of country in Virginia, 
the Carolinas, Georgia, and Alabama. Theso diluvial de- 
posits furnish nearly all the gold of commerce, by a process 
of washing, and amalgamation with mercury. Large masses 
of gold sometimes occur, as one of twenty-eight pounds in 
North Carolina, and in Siberia a mass was found, now in 
the Imperial Cabinet of St. Petersburg, weighing nearly 
eighty English pounds. Generally, however, iu occurs only 
in minute grains. It is also found in veins of quartz, in 
compact limestone, and distributed in iron pyrites. Native 
gold is usually alloyed with silver. 

653. Gold is distinguished by its splendid yellow color, 
its brilliancy, and freedom from oxydation, by its extreme 
malleability and ductility, by its high specific gravity, (19-26 
to 19-5,) and by its indifference to nearly all reagents. It 
fuses at 2016° F., and is dissolved only by aqua regia, 
(420,) by nascent cyanogen, and by selenic acid. The first 
is the solvent commonly known, and the solution contains 
the perchlorid of gold. 



What is the arbor Diana ? 652. How does gold occur in nature ? 
How is it obtained? 653. Describe this metal. What is its usual 
solvent ? 



346 METALLIC ELEMENTS. 

654. Gold forms two very unstable oxyds, (A.u 2 and 
Au 2 3 ,) which are decomposed, even by light. Two cor- 
responding chlorids exist. The perchlorid is a very deli- 
quescent salt, forming a red crystalline mass, soluble in 
ether, alcohol, and water. Metallic gold is deposited in 
elegant crystalline crusts from the ethereal solution of the 
chlorid. Ammonia throws down from solutions of gold an 
olive-brown powder, (fulminating gold,) which when dry 
explodes with heat, or by percussion. 

655. The solution of protosulphate of iron throws down 
gold from its solutions in a very fine brown powder, which 
is green, as seen by transmitted light, when diffused in water. 
The protochlorid of tin forms a characteristic purple pre- 
cipitate in gold solutions, called the purple of cassius, which 
is used in porcelain painting, and is probably a compound of 
the oxyds of tin and gold. Gilding of ornamental work is 
usually performed by gold leaf; but other metals are gilded 
either by applying it as an amalgam with mercury, the 
mercury being afterwards expelled by heat, or preferably by 
the new process of galvanic gilding from a solution of the 
cyanid of gold and potassium, (248.) Gold wash, as it is 
called, is applied by a mixture of carbonate of soda or potash 
in excess, with oxyd of gold, in which small articles cleansed 
in nitric acid are boiled, and thus become perfectly covered 
with a very thin film of gold. 

53. PLATINUM. 

Equivalent, 98.68. Symbol, PI. Density, 19.70 to 21-23. 

656. Platinum is a very remarkable metal, and if 

abundant would be extensively useful in domestic economy. 
It is found native in the gold workings in South America and 
in Siberia, on the eastern slope of the Urals. No ore of 
platinum is known, except its alloy with gold, and with 
iridium, osmium, and rhodium. 

Platinum is a white metal, between tin and steel in color, 
but harder than gold or silver, and unless quite pure, is, 
when unannealed, nearly as hard as palladium. A very 
little rhodium or iridium renders it more gray in color, and 

5 654. How many oxyds of gold are there ? Describe the per- 
chlorid. 655. What tests distinguish gold ? How is gilding 
effected ? 656. Where is platinum found ? 






PLATINUM. 347 

much harder. If pure it is very malleable, especially when 
hot, and can then be imperfectly welded. Its ductility and 
tenacity are remarkable ; but its most valuable property is 
its infusibility, which is so great that the thinnest platinum 
foil may be safely exposed to the most intense heat of a 
wind-furnace. It is soluble only by aqua regia, but alloys 
readily with lead, iron, and other base metals, so that great 
care is needed in using platinum vessels, not to heat them in 
contact with any metal or metallic oxyd with which they 
combine ; caustic potash, and phosphoric acid in contact 
with carbon, will also act upon platinum, at a red heat. 
This is a most useful metal to the chemist, and vessels of 
platinum are quite indispensable in the operations of analysis. 
Large retorts or boilers are made of it for the use of manu- 
facturers of sulphuric acid, which sometimes hold sixty or 
more gallons. In Russia it has been employed in coinage, 
for which by its great density and hardness it is well suited. 
When recently fused by the compound blowpipe or the gal- 
vanic focus, its density is about 19*9, which is increased to 
21-5 by pressure and heat. 

657. Platinum is obtained pure by digesting crude plati- 
num in aqua regia, and adding to the deep brown liquid a 
solution of chlorid of ammonium ; this throws down an orange- 
colored precipitate, which is a double chlorid of platinum 
and ammonium. This precipitate is reduced by heat to the 
metallic state, — a porous dull brown mass, commonly known 
as platinum sponge. All the platinum of commerce is treated 
in this way. The sponge is condensed in steel moulds by 
heat and pressure, and when compact enough to bear the 
blows of the hammer, is heated and forged until it is perfectly 
tough and homogeneous. 

Spongy platinum is a very remarkable substance, having, 
as already noticed, (397,) power to cause the combination of 
hydrogen and oxygen, and to effect other chemical changes 
without being itself altered. 

Platinum black is a still more curious form of metallic 
platinum, and is formed by electrolyzing a weak solution 
of chlorid of platinum, when the black powder of platinum 
will appear on the negative electrode. The silver plates in 
Smee's battery (247) are prepared in this way. It is also 

Describe its characters and uses. 657. How is it obtained from 
its ores ? What is platinum black, and what are its properties ? 



348 METALLIC ELEMENTS. 

prepared by adding an excess of carbonate of soda, with 
sugar, to a solution of chlorid of platinum, and gradually 
heating the mixture to near 212°, stirring it meanwhile. 
The black powder which falls is afterwards collected and 
dried. This powder has the property of causing union among 
gaseous bodies — as, for example, the elements of water — to a 
greater degree than the spongy platinum. 

658. Platinum forms two oxyds, and two chlorids, viz : 
PIO, P10 2 , and P1C1, P1CI 2 . The oxyds are prepared from 
the chlorids by precipitation with alkalies, and are very unsta- 
ble. The protochlorid is prepared by heating the bichlorid 
to 450°, when chlorine is evolved and it is left as a greenish- 
gray insoluble powder. 

The bichlorid of platinum is the usual soluble form of 
platinum, and is always formed when 'platinum is digested 
in aqua regia. It is prepared pure by dissolving spongy 
platinum in this menstruum, and cautiously expelling the 
acid by evaporation, at a moderate temperature. It gives 
a rich orange solution both in alcohol and water; and 
forms soluble salts of much interest, with many metallic 
chlorids. Those with the alkaline metals are the most im- 
portant. The double chlorid of platinum and potassium is 
a very sparingly soluble salt, (P1C1 2 ,PC1,) which falls as a 
yellow highly crystalline precipitate when chlorid of plati- 
num is added to a solution of chlorid of potassium. The 
double chlorid of sodium and platinum (PlCl 2 NaCl + 6HO) 
is on the other hand very soluble, and forms large beautiful 
yellowish-red crystals in a dense solution. Potash and 
soda are most easily separated, by the different solubility of 
their double chlorids. The double chlorid of ammonium and 
platinum (P1C1 2 NH 4 C1) is the orange precipitate before named, 
and is the only test required to determine with perfect cer- 
tainty the presence of platinum in a solution. 

54. PALLADIUM. 

Equivalent, 53-27. Symbol, Pd. Density, 11*8. 

659. This very rare metal is usually found associated 
with ores of platinum. It is also found alloyed with gold 

658. How is the bichlorid prepared ? Describe the double chlorids 
of platinum and the alkalies, their preparation and characteristics. 
659. W*iat is the symbol and equivalent of palladium ? 



RHODIUM, IRIDIUM. 349 

and silver in Brazil. It is a grayish-white metal, rather 
more brilliant than platinum, ductile, malleable, and extreme- 
ly infusible. It is, however, fused by the compound blowpipe. 
It gains a blue tarnish like steel by heating in the air, which 
it loses by a white heat. In hardness it is equal to fine steel, 
and it does not lose its elasticity and stiffness by a red heat. 
Its density varies from 10*5 to 11*8, and it suffers no change 
by exposure in the air. These qualities would render it a 
very valuable metal if it could be obtained in a sufficient 
quantity. Nitric acid dissolves it slowly, but aqua regia 
more rapidly. It forms two oxyds and two corresponding 
chlorids. 

55. RHODIUM. 

Equivalent, 52*4. Symbol, R. Density, 10*8. 

660. This is another metal associated with the ores of 
platinum, and is obtained by a process which need not be 
described here. It is a reddish-white metal, as fusible as 
iridium, and in hardness, ductility, and malleability, is much 
like it. Its density is probably about 10-8. (Hare.) 

56. IRIDIUM. 

Equivalent, 98- 68. Symbol, Ir. Density, 21-8. 

661. Iridium is also associated with the ores of platinum 
in the native alloy called iridosmine, or osmiuret of iridium, 
which is left in black shining scales as a residuum, after 
digesting platinum^ ores in aqua regia. Iridium when ob- 
tained pure and fused, is susceptible of a fine polish, has a 
pale antimonial whiteness and the fracture of cast-iron. It 
is somewhat ductile, as hard as unannealed steel, and fuses 
under the compound blowpipe. It is the densest body known, 
being as high as 21*80. (Hare.) The native alloy is much 
more infusible than the pure iridium, being, in fact, one of the 
most infusible bodies known ; it is very hard, and is used to 
point gold pens. Four oxyds and four chlorids have been 
described. 



Describe its properties? 660. What is said of rhodium? 661. 
With what metal is iridium associated ? What is its density and 
hardness ? 
30 



PART IV.— ORGANIC CHEMISTRY.* 

INTRODUCTION. 

1. General Properties of Organic Bodies. 

662. Definition. — Organic chemistry is confined to the 
study of those bodies which are the products of life, and to 
the changes which they suffer by the action of other sub- 
stances. 

663. The constituents of organic bodies are compara- 
tively few, but the results produced by their various combi- 
nations are wonderfully complex and numerous. Oxygen, 
nitrogen, carbon, and hydrogen, differently arranged and 
combined, compose nearly all the bodies found in the vege- 
table and animal kingdoms. Sulphur, phosphorus, and per- 
haps iron, occasionally occur, however, in these products ; 
and by the action of various reagents we are enabled to 
combine with organic substances, or with the products of 
their decomposition, chlorine, bromine, iodine, and various 
other bodies. In this way a great number of new com- 
pounds are produced, which come within the province of or- 
ganic chemistry as above defined. 

664. Both animals and vegetables contain salts of potash, 
soda, lime, magnesia, and iron, with sulphuric, phosphoric, and 
silicic acids, and chlorine. Animals also secrete phosphate 
and carbonate of lime, to form their bones, as in quadrupeds, 
and their external coverings, as in the mollusca. These salts 
have been already described under their proper heads, in the 
inorganic chemistry, and their relations to life will be con- 
sidered in the section on the nutrition of animals and plants. 

665. A strictly philosophical distinction cannot be estab- 
lished between organic and inorganic chemistry, as it will 
be seen from the statements already made, that these two 

* The questions at the foot of each page will be omitted in the 
remaining portion of the work, in the belief that both teacher and 
pupil will, by the time they reach this point, have become so familiar 
with the subject and with each other, as to render the questions no 
longer important, while the space which they occupy can be better 
employed. 



GENERAL PROPERTIES OF ORGANIC BODIES. 351 

departments shade into each other so gradually, that the 
line of division must of necessity be somewhat arbitrary. 

Formerly it was considered as a distinctive mark of or- 
ganic compounds, that they could not be artificially formed 
at will, from a combination of their constituents. This 
distinction is, however, no longer exclusively true, since 
we are now able to form urea from cyanic acid and ammo- 
nia, both of which may be derived from the reaction of the 
mineral ingredients. By peculiar processes we have also 
been able to form numerous other bodies which are the 
products of organic life. They are, however, comparatively 
simple in their composition, and occur in nature only as 
secretions of organized bodies.* No art can ever enable us 
to produce the simplest organized tissue, as a cell or a fibre. 

666. An important characteristic of organized bodies is 
the complexity of their composition, and their high equiv- 
alent numbers. In mineral compounds we rarely have any 
thing more intricate than a salt of two or three bases ; as for 
example, common alum, (568,) which may be resolved into 
sulphuric acid, alumina, potash, and water, each of which 
contains oxygen and a base. These constituents may be 
again combined to form the original alum. 

667. The substance called gelatine, which is a principal 
constituent of the cellular tissue in animals, has the formula 
C ]3 Hi N 2 O5. By the action of heat, or other agents, 
we are able to resolve this complex body into ammonia, 
water, and other compounds, which are very much more sim- 
ple than gelatine. And these again we may decompose 
into their constituent elements. But by no power at our 
command, can we join the dissevered elements to form ge- 
latine anew. This peculiarity of organization is dependent 
on the vital force, which modifies the chetnical affinities of 
bodies in a manner that we can never hope to imitate. While, 
therefore, in the study of mineral chemistry we can usually 
avail ourselves of the evidence to be obtained from both analy- 
sis and synthesis, (14,) in organic chemistry we must gener- 
ally be content with the former of these methods of proof. 

668. Organic bodies possess the further peculiarity, that 
carbon is almost invariably one of their constituents, and 

* Organized bodies, or organisms, are distinguished by having a 
structure, which is the result of life ; this, organic bodies do not 
necessarily possess. For example, horn and skin are organisms^ 
while gum and fat are simply organic bodies. 



352 ORGANIC CHEMISTRY. 

associated in such proportions with oxygen, nitrogen, and 
hydrogen, that when the body is burned, these last combine 
with it to form carbonic acid and carbureted hydrogen ; 
and also among themselves, producing water and ammonia ; 
while any excess of carbon remains behind as charcoal. 
Organic substances have for this reason been defined by 
some writers as those bodies which char or blacken by heat. 

2. Modes of Combination. 

669. The different combinations presented by ©rganic 
bodies may be reduced to three classes, and the laws which 
govern these will equally apply to all chemical compounds. 
These three modes of combination are termed, (1,) equiva- 
lent substitution ; (2,) substitution by residues, and (3,) 
direct union. 

670. (1.) Equivalent Substitution. — The statement of 
this law is that one or more equivalents of any element in a 
compound, may be replaced by the same number of equiva- 
lents of another element. For example, acetic acid, C 4 H 4 4 , 
by the action of chlorine gas loses three equivalents of hydro- 
gen, which go to form hydrochloric acid, and takes in their 
place three equivalents of chlorine, which are substituted for 
the hydrogen. The new product, (chloracetic acid, C 4 CI 3 H0 4 ,) 
closely resembles acetic acid in its properties. 

Chlorine can then replace hydrogen, and the same power 
is possessed by bromine and iodine. 

671. Alcohol, which has the formula QHgOa, may have 
its oxygen replaced by sulphur, yielding sulphur-alcohol, 
C 4 H 6 S 2 . Selenium and tellurium, which bear the closest 
resemblance in all their properties to sulphur, (250, iii.) 
can in the same manner replace oxygen. We see then that 
hydrogen may be replaced by chlorine, bromine, and iodine ,* 
and oxygen by sulphur, selenium, and tellurium. 

672. Where acetic acid acts upon metallic zinc, hydrogen 
is evolved and acetate of zinc (C 4 H 3 Zn0 4 ) is formed ; a com- 
pound in which an equivalent of zinc replaces one of hydro- 
gen. When this acid acts upon oxyd of zinc the acetate is 
also formed, while water is produced by the union of the 
oxygen of the oxyd with the hydrogen of the acid. Many 
chemists suppose that the acid contains water (thus C 4 H 3 3 
+ HO,) which is decomposed in the one case, and displaced 
by the oxyd in the other : but we cannot separate water from 
the acid and obtain the compound C 4 H 3 3 , and indeed, we 



MODES OP COMBINATION. 353 

have no proof of the existence of such a compound. The 
view just stated, explains the constitution equally as well as 
the old one, and avoids all hypothesis. 

673. From acetic acid we may form a great number of 
salts in which an equivalent of metal replaces one of hydro- 
gen, and the chloracetic acid yields a corresponding series. 
These constitute a genus, of which acetic acid is the type, 
and the various salts species. Thus — 

Acetic acid, C 4 H 4 4 Chloracetic acid, C 4 C1 3 H0 4 

Acetate of potash, C 4 H3K0 4 Chloracetate of potash, C 4 C1 3 K0 4 
Acetate of silver, C 4 H 3 Ag0 4 Chloracetate of silver, CiCl 3 Ag04 

In some compounds we can successively replace one, two, 
and even five equivalents of hydrogen by chlorine, or 
bromine, without deranging the molecular structure of the 
compound — in other words, without destroying its type. 

674. In the acetic and many other acids, but one equiva- 
lent of hydrogen can be replaced by a metal, so that the salts 
contain but one equivalent of base ; these acids are therefore 
called monobasic acids. In tartaric acid, C 8 H 6 12 , two equiva- 
lents of hydrogen may be thus replaced, and a salt obtained 
of the formula C 8 H 4 M a 12 , M standing for any metal. These 
two equivalents may be replaced by two different metals, as 
by potassium and sodium, C 8 H 4 KNaOi 2 ; and salts may also 
be formed in which but one equivalent of the hydrogen is 
replaced, as C 8 H 5 K0 12 . These are acid salts, having an acid 
reaction, and are still capable of neutralizing alkalies. Acids 
like the tartaric are called bibasic, and are distinguished both 
by yielding acid salts and by combining with, two bases. 
Tribasic acids are also known, which contain three equiva- 
lents of hydrogen, replaceable by a metal ; they can form three 
kinds of salts, in which one, two, and three equivalents of a 
metal are substituted for the same number of hydrogen. 
The two first of these salts are acid, the third is neutral. 

675. (2.) Substitution by Residues. — When nitric 
acid, NH0 6 =N0 5 + HO, acts upon the body called benzene, 
Ci 2 H 6 , two equivalents of its oxygen combine with the 
hydrogen of the benzene to form 2HO, and the residues unite 
to produce a new body, nitrobenzide, C 12 H 5 N0 4 , or C n U 4 
NH0 4 . Acetic acid and alcohol unite in the same way to 
form acetic ether, C 4 H 4 4 +C 4 H 6 2 ~2HO=C s H 8 4 . In 
these compounds the acids cannot be discovered by the usual 
tests. 

30* 



354- ORGANIC CHEMISTRY. 

From these and a great number of similar cases, we 
deduce the law, that in these reactions, a portion of the 
oxygen of one body combines with the hydrogen of the 
other to form water, which is set free, while the residues 
unite. In the formation of nitrobenzide NH0 6 — 2 is sub- 
stituted for H 2 in the benzene. This principle explains in a 
simple manner many reactions in chemistry, and admits of a 
great number of applications, some of which we shall 
mention in their appropriate places. 

676. The student is now prepared to understand the 
formation of the sesqui-salts. In those salts, which corres- 
pond to oxyds with one equivalent of oxygen, the metal re- 
places the hydrogen, equivalent for equivalent ; thus acetic 
acid is C 4 H 4 4 , and acetate of iron, C 4 H 3 Fe0 4 ; but three 
equivalents of acetic acid react with one of sesquioxyd of 
iron to form one of sesquiacetate of iron and three of water ; 
three equivalents of hydrogen are removed, and but two of 
iron combined in their place. One equivalent of sesquiacetate 
of iron contains C^HgFeaO^, while three of the acetate equal 
C 12 H 9 Fe 3 0, 2 . The reaction which produces this seeming 
anomaly is readily explained: the three equivalents of oxgen 
in the sesquioxyd Fe 2 3 unite with three of the hydrogen of 
the acid, to form 3HO, and the residue Fe 2 replaces H 3 . 

677. (3.) The third mode of combination in compounds is 
that of direct union, as when chlorine and sodium unite to 
form common salt. We have in organic chemistry examples 
of this mode in the vegetable alkalies which unite directly 
with acids and metallic salts ; also in some organic products 
which combine in the same manner with chlorine. 



3. Isomerism. 

678. We have seen H«at acetic acid may have its 
hydrogen replaced by chlorme, while the characters of the 
compound remain unaltered. From this and similar in- 
stances we are led to conclude that the properties of com- 
pounds depend rather upon the peculiar arrangement of their 
constituent atoms than upon their kind : and moreover that 
the same proportions of the same elements may by a different 
mode of union form compounds widely differing in their 
characters. Such is really the case ; there are many in- 
stances of substances which, possessing the same composition 
and equivalent, are yet perfectly distinct in their properties. 



ON THE DENSITY OF Vai'ORS. 355 

The formic ether of alcohol, and the aceti<K ether of wood 
spirit, are represented by the same formula, i. e. C 6 H60 4 , 
but are very different in respect of many of their properties ; 
from the manner of their formation and the products of their 
decomposition, we have evidence of a difference in the 
arrangement of their molecules. Substances which have 
the same equivalent composition, but which differ in their 
properties, are called isomeric, or more definitely metameric 
bodies.* 

679. Another form of isomerism is that in which the 
relative proportions of the elements being the same, one sub- 
stance has double or triple the equivalent of the other. The 
oil of bitter almonds and benzoine may both be represented 
by C 14 H 6 2 , but the equivalent of the last is double that of 
the oil, and its real formula is C^H^C^. This relation is 
called polymeric, and benzoine is said to be polymeric of 
bitter almond oil. 

The compounds of carbon and hydrogen present many 
remarkable instances of isomerism ; olefiant gas, C 4 H 4 , buly- 
rene, C 8 H 8 , naphtene, C 16 H 16 , and cetene, C^ft^, have the same 
proportions of carbon and hydrogen, and each of these is 
polymeric of these before it. The equivalents of those 
bodies are determined from an examination of their com- 
binations with other substances, or from the density of their 
vapors. 

4. On the density of vapors. 

680. It has been already shown that bodies unite in 
certain proportions by volume as well as by weight, (190,) and 
that where a condensation follows the union, it is always one- 
third, one-half, or some other simple proportional to the sum 
of the volumes of its constituents. The vapor of water 
contains two volumes of hydrogen, and one of oxygen, con- 
densed one-third, and its specific gravity is equal to one-half 
the sum of the specific gravities of its constituents, thus — 
69*3 is the density of hydrogen, air being 1000, and on the 
same scale the density of oxygen is 1109-3, then — 

* Isomerism, from isos, equal, and meros, measure, may be employed 
to designate all cases in which the same elements exist in the same 
relative proportions ; while metamerism, from meta, by, and meros, 
implies that the proportions of the elements are not only relatively 
but absolutely the same. The term polymerism, from polus, many, 
and meros, is explained oy the examples given in (679.) 



356 ORGANIC CHEMISTRY. 

Two volumes of hydrogen, 2 X 69-3 = 138-6 

One " oxygen, = 1109-3 

Two " water, = 1247-9 



One " " = 623-9 

Now the specific gravity of the vapor of water at the 
normal temperature and pressure (120 and 131,) is 620*1, 
air being 1000, consequently if we know (192) the com- 
bining volume of any vapor, or the volume of its elements 
and its density, we can calculate the number of equivalents 
of each element in the compound, or in other words we can 
ascertain its formula. For example, olefiant gas has a specific 
gravity of 971, air being 1000, and it is composed of equal 
equivalents of carbon and hydrogen ; one volume of it 
contains — 

One volume of carbon vapor,* = 832-0 

Two volumes hydrogen, 2X69-3 = 138-6 



Yielding one volume of olefiant gas, 970-6 

As we know from its compounds that the equivalent of 
this gas is represented by four volumes, its formula must be 
C 4 H 4 . The vapor of butyrene has a density of 1926 ; and as 
its combining volume is the same as olefiant gas, its formula 
will be C 8 H 8 . Cetene, C 32 H 32 , has a density eight times that 
of olefiant gas. 

681. The determination of the density of vapors is of 
great importance: in case of some volatile organic com- 



* As carbon is not volatile, the density of its vapor cannot be de- 
termined directly ; in its gaseous compounds, however, we know 
that it must assume the gaseous form. Now carbonic acid contains 
a volume of oxygen equal to its own ; if then from the number ex- 
pressing its specific gravity, we deduct that of oxygen, we shall 
have the specific gravity of the carbon vapor. 

The density of carbonic acid is 1525-2 air 1000 

Deduct oxygen, 1109-3 



We have the density of carbon vapor, 415-9 
If we assume that the acid contains two volumes of oxygen gas" 
and one of carbon, (C0 2 ) condensed into two volumes, the density 
of the vapor will be 415-9 X 2=831-8. It is not improbable, how- 
ever, that the acid may consist of equal volumes of carbon vapor 
and oxygen condensed one-half; in which case the density of tne 
former will be 415-9, and its volume the same as hydrogen; two 
volumes corresponding to an equivalent. 




ANALYSIS OF ORGANIC SUBSTANCES. 357 

pounds which form no combinations with other substances it 
is the only means of ascertaining their constitution and 
equivalent. The process is very simple ; the method em- 
ployed in case of gases has been already described, (49.) 
When the substance is a liquid or solid, it is introduced into 
a narrow-necked glass globe of the form represented in the 
annexed figure, the weight of which is care- 
fully ascertained. The globe is held by 
means of its handle firmly attached by wire, 
beneath the surface of an oil or water-bath, 
and then heated to some degrees above the 
boiling-point of the substance. When this is 
all volatilized and the globe is filled with the 
vapor, the open and projecting end of the 
globe's neck is sealed by the flame of a spirit 
lamp ; and at the same time, the temperature 
of the bath is noted. When the globe is cooled 
it is again weighed, and the end of the neck 
broken off beneath the surface of mercuy, which 
rushes up and fills the vacuous vessel. The 
■mercury is then carefully measured. The capacity of the 
vessel and its weight being thus ascertained, we can find the 
weight of a volume of vapor at the observed temperature, 
and by an easy calculation can determine what would be its 
volume at the ordinary temperature, (88) ; its weight com- 
pared with that of the same volume of air gives the specific 
gravity required. 

ANALYSIS OF ORGANIC SUBSTANCES. 

682. The ultimate analysis of organic substances is of 
great importance ; for as we are unable to form them by a 
direct combination of their elements, a correct understanding 
of their composition and of the nature of the changes which 
they undergo, must depend entirely on the results of their 
analysis. The equivalent of many substances is so large,' 
that a change of one-hundredth part in the proportions, gives 
to the compound entirely distinct properties. Great refine- 
ment is consequently necessary in analysis, to enable us to 
detect the minute differences in composition, and such have 
been the care and skill with which the subject has been 
studied, that we have now arrived at a surprising accuracy 
in operations of this kind. 



358 ORGANIC CHEMISTRY. 

683. In theory, the process of organic analysis is ex- 
ceedingly simple. If any organic substance, as sugar, for 
example, is heated with a body capable of yielding oxygen, 
such as the oxyd of copper, lead, or any other easily re- 
ducible metal, it is completely decomposed ; the carbon and 
hydrogen take oxygen from the metallic oxyd, and are wholly 
converted into carbonic acid and water. From the weight 
of these, it is easy to calculate the amount of carbon and 
hydrogen in the body, and if it contains no other element 
except oxygen, this is known by the loss. But notwith- 
standing the theoretical simplicity of the process, its execution 
is exceedingly difficult, and very many precautions are ne- 
cessary to insure accuracy. It is not the object of this work 
to explain all the precautions necessary to the successful per- 
formance of analytical operations, but merely to give an 
outline of the method pursued, and a general idea of the 
means employed. For more particular information the 
student is referred to an excellent memoir on this subject, by 
Baron Liebig. 

684. The operation is performed in a combustion tube of 
hard glass, about 12 inches in length, and from -^ to T 5 -g- of 
an inch in diameter. One end is drawn out to a point, 
turned aside and sealed. Oxyd of copper prepared from the 
nitrate (609) is generally employed for the combustion. 
Just before using it, it is heated to redness, in order to expel 
the moisture which it readily attracts from the atmosphere ; 
the combustion tube is then about two-thirds filled with the 
hot oxyd. The substance to be analyzed having been care- 



\ 



1 - i i 

Oxyd. Mixture. Oxyd. 

fully desiccated, five or six grains of it are weighed out in a 
tube with a narrow mouth, in order to prevent the absorption 
of moisture. It is then rapidly mixed in a dry porcelain 
mortar, with the greater portion of the oxyd from the tube, 
to which it is again transferred, and the tube is then nearly 
filled up with pure oxyd. The relative portions of the oxyd 
and mixture are shown in the figure above. 

685. However carefully the mixture has been made, a 



ANALYSIS OF ORGANIC SUBSTANCES. 359 

9 

little moisture will have been absorbed from the air, which 
must be removed by the following arrangement. To the 
end of the combustion tube is fitted, by means of a cork, a 
long tube filled with chlorid of calcium, and to this is attached 
a small air-pump. The combustion tube is covered with hot 
sand, and the air slowly exhausted. After a short time, the 
stopcock is opened, and the air allowed to enter, thoroughly 




dried by its passage over the chlorid of calcium. It is again 
exhausted, and this process repeated four or five times, by 
which the mixture is completely dried. The annexed figure 
shows the arrangement for this purpose. 

686. The tube is now ready for the combustion, and is 
placed in the r ===—_=—___ 



furnace repre- 
sented m the 



^^^Sffl 



accompanying 
figure. It is 

constructed of sheet iron, and fitted with a series of sup- 
porters at short distances from each other, to prevent the tube 
from bending when softened by heat. The furnace is 
placed on a flat stone or tile, with the front slightly inclined 
downwards. The quantity of water formed in the process 
is estimated by a light tube, represented in the annexed 
figure, which is filled with — ,, 

fragments of chlorid of ^ 

calcium, and after having been very carefully weighed, is 
attached by a well dried and closely fitting cork, to the end 
of the combustion tube. To determine the carbonic acid, 
a small five-bulbed tube of peculiar form, called Liebig's 



360 ORGANIC CHEMISTRY. 

• 

potash bulb, and represented in the annexed 
figure, is used. It is charged for this pur- 
pose with a solution of caustic potash of a 
specific gravity about 1*25, with which the 
three lower bulbs are nearly filled. Its weight 
is determined with great exactness, and it is 
then attached to the chlorid of calcium tube, 
by a little tube of gum elastic, which is held 
fast by a silken cord. The whole arrange- 
ment is shown below. The tightness of the junction is as- 
certained by drawing a few bubbles of air through the end 





of the potash tube, so that the liquid will be raised a few 
inches above the level on the other side ; if this level remains 
the same for some minutes, the whole apparatus is tight. 

687. Heat is now applied by means of ignited charcoal 
placed around the anterior portion of the tube, and when 
this is red-hot, the fire is gradually extended along the tube, 
by means of a moveable screen, represented in the figure. 
This must be done so slowly as to keep a moderate and uni- 
form flow of gas through the potash solution. When the 
whole tube is ignited, and gas no longer escapes, the closed 
end of the combustion tube is broken off, and a little air 
drawn through the apparatus to remove all the remaining 
products of combustion. The tubes are then detached, and 
from the increase of weight in the chlorid of calcium tube, 
the amount of water, and hence that of hydrogen, is deduced. 
The carbon is determined from the increase in weight of the 
potash bulbs, by a simple calculation. 

688. Volatile fluids are analyzed by enclosing them in a 
narrow-necked bulb of thin glass, filled with the fluid in the 
same mode as thermometers, (76.) The weight of the 
empty tube is first ascertained ; the fluid is introduced, the 
neck sealed, the weight being again ascertained, and the 




ANALYSIS OF ORGANIC SUBSTANCES. 361 

difference gives the weight of the fluid. 
The neck of the bulb is then broken 
by a file mark at a, dropped into the 
closed end of the combustion tube, and 
covered with oxyd of copper, which 
should nearly fill the tube. When this 
is heated to redness, a gentle heat ap- 
plied to the portion of the combustion Q 
tube containing the volatile fluid, sends 
it in vapor over the ignited oxyd, completely burning it. The 
products of its combustion are estimated as before. 

689. Fatty bodies and others which contain much car- 
bon and a small quantity of hydrogen, are more perfectly 
burned by employing chromate of lead in place of the oxyd 
of copper. This substance does not readily attract moisture 
from the atmosphere, like oxyd of copper, and is consequently 
better when the hydrogen is to be determined accurately. 
The chromate of lead (595) is prepared for use by heating 
it until it begins to fuse, and when cool reducing it to powder. 

690. When nitrogen is a constituent of organic bodies, 
it is determined by placing in one end of the combustion 
tube, about three inches of carbonate of copper, secured in 
its place by a plug of asbestus ; and then the nitrogenous 
body is introduced, mixed with oxyd of copper. The re- 
maining space in the combustion tube is filled with turnings 
of metallic copper. The air is then withdrawn by an air- 
pump, and a gentle heat applied to the carbonate of copper, 
which evolves carbonic acid, and drives out all remaining 
traces of common air. The tube is now heated as usual, 
and the gases evolved are collected in a graduated air-jar, 
over mercury. When the combustion is finished, heat is 
again applied to the carbonate of copper, and another portion 
of carbonic acid expelled, which drives out all the nitrogen 
from the tube. The use of the copper turnings is to decom- 
pose any traces of nitric oxyd, which may be formed in the 
process. The carbonic acid is removed from the air-jar, by 
a strong solution of potash, and pure nitrogen remains, 
which is measured with the usual precautions, and from its 
volume the weight is easily determined. 

691. Another and a preferable mode of determining nitro- 
gen, is that of Will and Varrentrapp, which is founded on 
the fact that when a body containing nitrogen is heated with 
an excess of caustic potash, or soda, all the nitrogen is 

31 



362 • ORGANIC CHEMISTRY. 

evolved in the form of ammonia, and may be thus estimated, 
by conducting it into hydrochloric acid. 

692. Chlorine is determined in the analysis of organic 
compounds, by passing the vapor over quick lime heated to 
redness in a combustion tube ; chlorid of calcium is formed, 
which is afterwards dissolved in water, and the chlorine pre- 
cipitated by nitrate of silver. From the weight of the chlorid 
of silver, the amount of chlorine is calculated. 

693. Sulphur is a rare constituent of organic compounds. 
Its presence is detected by fusion with nitre and carbonate of 
soda, or by digestion with nitric acid. Sulphuric acid is thus 
formed, and is precipitated as sulphate of baryta, from the 
weight of which, that of the sulphur is determined. In the 
analysis with oxyd of copper, a small tube of peroxyd of 
lead is introduced between the chlorid of calcium tube and 
the potash apparatus, to absorb the sulphurous acid which is 
evolved. 



ORGANIC COMPOUNDS AND PRODUCTS OF THEIR 
ALTERATION. 

AMMONIA, NH 3 . 

694. The properties of ammonia and of its salts have been 
already described, (438.) It is a constant product of the 
decomposition of all organic matters which contain nitrogen ; 
and carbonate of ammonia is obtained in large quantities 
in the dry distillation of horns, bones, and other animal 
substances. When any nitrogenous organic substance is heated 
with an excess of hydrate of potash, its carbon is oxydized 
by the oxygen of the water, and all the nitrogen combining 
with the hydrogen is evolved in the form of ammonia. 

695. An equivalent substitution (438) of chlorine, 
bromine, or iodine, may be made for the hydrogen of ammo 
nia, with the production of interesting compounds. Thus 
when a jar of chlorine is inverted in a solution of an ammo- 
niacal salt, the gas is absorbed and a heavy yellow oily fluid 
separates, which is known as chlorid of nitrogen, NC1 3 : 
it is formed from ammonia by the substitution of chlorine for its 
hydrogen. This is a most explosive and dangerous body. 
Even a gentle heat, the contact of phosphorus, fat oils, and many 
>ther agents, cause it to be decomposed with a very violent 

xplosion. Bromine forms an analogous compound, (NBr 3 .) 



AMMONIA. " 363 

The reaction of ammonia with iodine, (when these two sub- 
stances are triturated together,) produces a compound in 
which two of its equivalents of hydrogen are replaced by 
iodine, giving us the formula, NI 2 H. It is a heavy black 
powder, which can hardly be dried from the ammoniacal 
liquor, without explosion, and which the slightest friction causes 
to be decomposed with a violent detonation. These bodies 
may be called tri-chlorinized and bin-iodized ammonia. 

Potassium when heated in dry ammonia displaces one 
equivalent of hydrogen, forming NH 2 K. This is an olive- 
green mass, which is resolved by water into ammonia and 
potash, NH 2 K + HO = NH+KO. 

696. Ammonia is largely absorbed by many metallic 
salts, and forms with them definite crystalline compounds ; 
for example, the salts of silver, copper, and zinc combine 
with two equivalents of ammonia : but the affinity which 
holds the ammonia is feeble, and it may be often expelled 
from these combinations by a gentle heat. In some instances, 
however, the action is different ; thus when ammonia is added 
to a solution of chlorid of mercury, a white precipitate is 
formed, which appears to be a compound of HgCl with 
NH 2 Hg, corresponding to the potassium compound just 
described, HgCl + NH 3 == NH 2 Hg + HC1. The hydrochloric 
acid combines with another portion of ammonia to form sal- 
ammoniac. When a solution of ammonia is digested with 
calomel (Hg^l) a black powder is formed, the composition 
of which may be represented by Hg 2 Cl + NH 2 Hg 2 . This 
reaction is like the last ; the chlorine unites with one equiva- 
lent of hydrogen, which is replaced by the residue Hga. 
These are examples of the substitution by residues, (675.) 

697. Amides. — The action of ammonia upon many orga- 
nic substances containing oxygen is peculiar ; one, two, or 
three of its equivalents of hydrogen combine with the oxygen 
of the organic body, and the residues unite. Compounds are 
thus produced in which NH 2 , NH, or N replace the whole or 
a part of the oxygen of the organic compound. To these the 
name of amides has been given. Neither ammonia nor the 
organic matter can be detected in such compounds by the 
usual tests, but by the aid of acids and heat they take up the 
elements of water and reproduce the original substances ; the 
ammonia combining with the acid, while the organic body is 
set free. When the organic substance forming the amide is 
an acid, a similar change is effected by a solution of an 



364 



ORGANIC CHEMISTRY. 



alkali ; the regenerated acid forms a salt with the alkali, and 
ammonia escapes. 

698. The amides of monobasic acids are derived from one 
equivalent of the acid and one of ammonia, by the loss of 
two equivalents^ of water. The bibasic acids afford twc 
amides corresponding to their neutral and acid salts. (674.* 
These may often be formed by the action of heat upon the 
ammoniacal salts, which are resolved into water and an 
amide. Thus the oxalate of ammonia, when heated, loses 
four equivalents of water and is converted into oxamide, C 4 H 2 
8 + 2NH 3 (oxalate of ammonia) = 4HO + C 4 H 4 N 2 4 . This 
is a neutral insoluble body, which is converted into oxalic 
acid and ammonia by solutions of both alkalies and acids. 
The acid oxalate of ammonia, C 4 H 2 8 + NH 3 , loses in the 
same manner two equivalents of water and yields oxamic 
acid, C 4 H 3 N0 6 . This is a monobasic acid, and yields a series 
of salts ; it is, however, a proper amide, and is decomposed 
by the same agents as oxamide. When boiled for some time 
with water it takes up the elements of two equivalents, and is 
converted into acid oxalate of ammonia. 



THE GROUP OF ALCOHOLS AND THE PRODUCTS OF 
THEIR ALTERATION. 



ALCOHOL, C 4 H 6 2 . 

699. This important substance is a product of the fermen- 
tation of sugar, and is contained in all fermented liquors. 




ALCOHOL. 365 

From these it is obtained by distillation. A convenient appa- 
ratus for condensing the vapor of alcohol, ether, and other 
volatile products of distillation, is represented in the foregoing 
figure. The general arrangement is similar to the usual dis- 
tillatory apparatus, (117.) The neck of the retort passes 
into a large glass tube, which is encased by an outer one of 
metal closely adapted by corks at its ends to the glass tube, 
leaving a water-tight cavity between the two, which is filled 
with cold water by a tube entering near the lower end and 
terminating in a funnel at a higher level, where water is sup- 
plied from a small tank with a cock. An orifice near the 
upper end of the condenser permits the water to escape when 
it has risen to a higher level in the upper tube. This arrange- 
ment, (called from its inventor a " Liebig's condenser") secures 
an uninterrupted flow of cold water into the condenser 
as fast as the heated water escapes from the upper end, and 
the most volatile vapors are easily condensed to liquids in such 
an apparatus. If necessary, iced water can be employed. 
Alcohol thus distilled, still retains fifteen per centum of water. 
This is removed by digestion with quick lime or chlorid of 
calcium, which unite with the water, and another distillation 
yields anhydrous or absolute alcohol. 

700. Pure alcohol is a colorless fluid, with a specific gra- 
vity of *795, and boils at 173° F. It has a pungent and 
agreeable taste, and a fragrant odor. It is very combustible, 
and burns with a pale blue flame without smoke, which ren- 
ders it very useful as a source of heat in chemical processes. 
The action of alcohol on the system, is well known as that of 
a powerful and dangerous stimulant. It is largely used in 
the operations of the arts, the preparation of medicines, and 
the processes of chemistry. Its solvent powers are very 
great ; the volatile oils and resins are dissolved by it, as well 
as many acids and salts, the caustic alkalies, and a largo 
number of other substances. 

The specific gravity of the vapor of alcohol is 1600, air 
being 1000; and its equivalent is represented by four vol- 
umes, oxygen being one. It is composed of 

4 volumes of carbon vapor, 4 x *832 = 3-3280 

12 « hydrogen, 12 X "0693 = -8316 

2 « oxygen, 2x1*1093 = 2-2186 



Equal to four volumes of alcohol vapor, 6-3782 

Of which one volume weighs, 1-3946 

31* 



366 ORGANIC CHEMISTRY. 

701. Sulphur Alcohol, Mercaptan, C 4 H 6 S 2 . — This singu- 
lar compound is alcohol in which sulphur replaces the oxygen. 
It is a colorless and very volatile fluid, and has a very pow- 
erful odor, resembling onions. It acts upon oxyd of mercury 
with great violence ;* water is formed, and a white crystal- 
line substance, which is C 4 H 5 HgS 2 . Analogous compounds 
may be obtained by its means with other metallic oxyds, and 
the term mercaptides has been used to distinguish them. 
Mercaptan is a fine example of the equivalent substitution of 
sulphur for oxygen in organic compounds. Mercaptan may 
be procured by saturating a solution of caustic potash, (den- 
sity of 1*3,) with sulphureted hydrogen gas, and distilling 
this in a retort with an equal volume of sulphovinate of 
lime of the same density. The regulated temperature of a 
salt bath, and a Liebig's condenser are necessary, and the 
mercaptan is separated by a funnel from the accompanying 
water, which collects with it in the cold condenser. 

Action of Acids upon Alcohol. 

702. Ethers. — The action of acids upon alcohol is highly 
important in relation to chemical theory, and has been very 
attentively studied. When a monobasic acid acts upon alcohol 
a combination takes place, with the elimination of two equiva- 
lents of water. The resulting compounds are called ethers, 
and have been considered as salts, in the formation of which 
alcohol minus one equivalent of water plays the part of a 
metallic oxyd. Unlike saline combinations, however, the 
acids of the ethers cannot be recognised by the usual tests : 
for example, oxalic ether does not produce any precipitate in 
the solutions of a salt of lime, while all the oxalates precipi- 
tate lime from its solutions as insoluble oxalate. When 
heated with the solution of a fixed alkali, the ethers take up 
the elements of two equivalents of water, regenerating alcohol 
and the acid. This change is sometimes effected by boiling 
with water. 

703. A bibasic acid reacts in the same manner with two 
equivalents of alcohol and the separation of four equivalents 
of water. Thus oxalic acid, C 4 H 2 O g , and two of alcohol, 
2C 4 H 6 2 , yield one equivalent of oxalic ether and four of 
w^ater, Ci 2 H 10 O 8 + 4HO. Often, however, the reaction is dif- 
ferent ; an equivalent of the acid acts upon but one equivalent 

* Whence its name, Mercuritim captans. 



ALCOHOL. 367 

of alcohol, and produces an acid ether which is capable of 
neutralizing bases to form salts. These are called vinic 
acids, and are monobasic ; e. g. oxalovinic and sulphovinic 
acids. If we represent the residue C 4 H 6 2 — H 2 by E, the 
composition of these compounds may be represented thus — 

Oxalic acid, C 4 H20 8 

Oxalic ether, C 4 H 2 \ 2 4 

I H,2 

Oxalovinic acid, C 4 H 2 \ -J* 
( 

In these compounds the residue represented by E replaces 

two equivalents of oxygen. 

704. Tribasic acids in the same way form neutral ethers 
with three equivalents of alcohol, or bibasic acids, with one 
equivalent. The power of forming vinic acids or acid ethers 
with alcohol, belongs only to those acids which are polybasic ; 
and the study of these reactions has shown us that several 
acids usually considered as monobasic are really bibasic 
acids. Thus the sulphuric yields with alcohol sulphovinic 
acid, with wood-spirit, (a compound closely allied to alcohol 
in its chemical relations,) a corresponding acid, and a neutral 
ether. Agreeably to this view the formula of sulphuric acid 
must be doubled— thus S 2 H 2 8 =2SH0 4 , or 2S0 3 HO. It will 
be remembered that this acid forms both neutral and acid 
salts, as well as salts with two fixed bases, and is for this 
reason also to be considered bibasic, (674.) Carbonic acid 
is in the same way bibasic, since it forms neutral and acid 
carbonates, and yields with alcohol carbonic ether, and car- 
bovinic acid. Nitric acid on the other hand yields a neutral 
ether with one equivalent, of alcohol ; it never forms acid or 
double salts, and is an example of a monobasic acid. 

The vinic acids and those formed in a similar manner are 
conveniently designated as coupled acids. 

705. In these coupled acids, as in the neutral ethers, the 
original acid cannot be detected by the usual tests. The sul- 
phovinate of baryta is a very soluble salt, while the sulphate 
of the same base is a very insoluble compound. When 
heated with hydrate of potash, the sulphovinates assume the 
elements of water, and regenerate the acid and alcohol. 

It will be observed that the ethers present many analogies 
to the amides in formation and composition, as well as in the 
mode of their decomposition by alkalies. The similarity of 
origin will be seen by comparing the oxalic ether and amides 



368 ORGANIC CHEMISTRY. 

Oxamide, C 4 H 2 N 2 04 = C 4 H 2 8 +2NH3— 4HO 

Oxalic ether, C 12 H 10 O 8 = C 4 H 2 8 + 2C 4 H602— 4HO 

Oxaraicacid, C 3 H 3 N0 6 = C 4 H 2 8 + NH3— 2 HO 

Oxalovinic acid, C 8 H<;0 8 = C^Og + C 4 H 6 02— 2H0 

The neutral ether and amide are derived from one equiva- 
lent of the acid, and two of ammonia or alcohol, by the loss 
of four equivalents of water ; and the oxamic and oxalovinic 
acids, which are monobasic, are in like manner formed from 
an equivalent of the bibasic acid and one of ammonia or 
alcohol, by the abstraction of two of water. 

706. Nitric Ether, C 4 H 5 N0 6 . — This compound is formed 
by distilling equal parts of strong nitric acid and alcohol 
with a few grains of urea. The action of nitric acid upon 
alcohol is very violent. Nitrous acid is formed, which de- 
composes the ether, and gives rise to a variety of products ; 
but a little urea prevents this, and the distillation proceeds 
quietly, yielding nitric ether and water, C 4 H 6 2 4-NH0 6 = 
2HO -f- C 4 H 5 N0 6 . It is a colorless liquid of a very sweet 
taste, is insoluble in water, has a specific gravity of 1*112, 
and boils at 185° F. The vapor explodes by a mod- 
erate heat. When this ether is mixed with a solution of 
potash in dilute alcohol, it reassumes the elements of water, 
and yields alcohol and nitrate of potash. 

707. Perchloric Ether, C 4 H 5 C10 S . — This is an extremely 
explosive compound, which is produced from the distillation of 
a concentrated solution of perchlorate and sulphovinate of 
barytes, in equivalent proportions. So long as the salts re- 
main in solution no reaction occurs, but as soon as they 
become solid a reciprocal decomposition ensues, and a sweet 
ethereal liquid collects in the receiver. This is the compound 
which has been called perchloric ether by Messrs. Hare and 
Boye.* It is a transparent colorless liquid, heavier than water, 
with a pungent agreeable smell, and very sweet taste, which 
leaves a biting impression on the tongue, similar to that of 
oil of cinnamon. It explodes by ignition, friction, or percus- 
sion, sometimes with no assignable cause, and with such pecu- 
liar violence that the smallest drop of it, when exploded upon 
an open porcelain plate, will shatter it into fragments. It is 
unsafe to operate with it unless protected by gloves and a close 
mask with thick glass eye-holes, and with the intervention of 
a moveable wooden screen. It dissolves in alcohol, and an 

* American Journal of Science, (1st Series,) vol. 42, p. 62. 



ALCOHOL. 369 

alcoholic solution of potash added to the solution of the 
ether in alcohol decomposes it, with the production of in- 
soluble perchlorate of potash. 

708. Hydrochloric Ether, C 4 H 5 CI. — This substance is 
obtained by saturating alcohol with hydrochloric acid gas, when 
the ether passes over, and must be condensed by a freezing 
mixture, C 4 H 6 2 + HC1=C 4 H 5 C1 + 2H0. It j s a colorless, 
very volatile liquid, with a pungent aromatic odor, and is 
slightly soluble in water. It has a specific gravity of *873, 
and boils at 52° F. With a solution of potash it is decom- 
posed like all the other ethers, and yields chlorid of potassium 
and alcohol. 

709. Hydrobromic Ether, C 4 H 5 Br. — When a mixture of 
alcohol, bromine, and phosphorus is distilled, hydrobromic 
acid is formed, which reacts with the alcohol to form hydro- 
bromic ether. It is a volatile fluid, heavier than water, and 
closely resembles the hydrochloric ether. 

Hydriodic Ether, C 4 H 5 I, is obtained by substituting iodine 
for bromine in the last process. It is a colorless liquid, of 
specific gravity 1*92, and boils at 160°. 

710. Acetene, C 4 H 6 . — When hydrochloric ether is decom- 
posed by potassium, chlorid of potassium is formed, and a 
white crystalline compound, which is C 4 H 5 K. This is 
decomposed by water, into water and a volatile oily liquid, 
which is C 4 H 6 . To this the name of acetene is given. The 
bodies formed by the action of hydrochloric, hydrobromic, 
and hydriodic acids upon alcohol, and which have just been 
described as ethers, may be viewed as acetene, in which an 
equivalent of hydrogen is replaced by chlorine, bromine, or 
iodine. A peculiar compound formed by the action of nitric 
or nitrous acid upon alcohol, may be viewed as a derivative 
of acetene. 

Nitric Acetene; Nitrous Ether; Hyponitric Ether, 
C 4 H 6 N0 4 . — The red vapors evolved by the action of nitric 
acid upon starch, are rapidly absorbed by dilute alcohol, 
with the evolution of heat, and the present compound passes 
off in vapor and may be condensed. It is a pale yellow 
fluid, of a very fragrant odor of apples ; it has a specific 
gravity of *947, and boils at 62°. This substance is re- 
garded by many as the ether of hyponitric acid, but it 
does not appear to yield alcohol and a hyponitrate by the 
action of potash, as it should do if it were like the ethers. 
It results from the action of N0 3 +C 4 H 6 2 =HO + C 4 H 5 N0 4 ; 



370 



ORGANIC CHEMISTRY. 



and may be regarded as derived from acetene and nitric 
acid, by the abstraction of 2HO. This substance is formed 
among many others, when alcohol is acted on by nitric acid, 
and an alcoholic solution of the impure product constitutes the 
sweet spirits of nitre, used in medicine. It was formerly 
obtained by distilling a mixture of nitre with sulphuric acid 
and alcohol. 

711. Sulphovinic Acid, C 4 H 6 S 2 8 . — The proper sulphu- 
ric ether, with two equivalents of alcohol, has not been 
obtained. When equal weights of alcohol and sulphuric 
acid are mixed and heated to boiling, sulphovinic acid is 
formed, and remains in the fluid ; the mixture is allowed to 
cool, diluted with water, and neutralized with chalk. The 
excess of sulphuric acid forms an insoluble sulphate with the 
lime, while the soluble sulphovinate of lime remains in solu- 
tion, and is obtained in crystals by evaporation and cooling. 
It forms beautiful colorless prisms, which have the composi- 
tion C 4 H 5 CaS 2 8 -f 2aq; they lose the water in a dry 
atmosphere. The sulphovinate of potash is obtained by de- 
composing the lime salt with carbonate of potash. 

If carbonate of baryta is substituted for chalk in neutral- 
izing the acid mother-liquor, sulphovinate of baryta may 
be obtained in fine crystals. From a solution of this salt, 
dilute sulphuric acid precipitates all the baryta, and a solution 
of sulphovinic acid is obtained, which may be concentrated 
in vacuo. It forms a sour syrupy liquid, which is decom- 
posed by a gentle heat, (or even by too much concentration,) 
into alcohol and sulphuric acid. 

712. Sulphovinic acid is derived from one equivalent of 
sulphuric acid, and one of alcohol, by the abstraction of the 
elements of two equivalents of water, 8211208-1-0411602 = 
C 4 H 6 S 2 8 + 2HO, and in its decomposition it reassumes the 
2H0. When a sulphovinate is distilled with hydrate of pot- 
ash, it yields alcohol and a sulphate of potash ; if, in place of 
hydrate of potash, the hydrosulphuret is employed, sulphur 
alcohol is obtained; C 4 H 6 S 2 8 +KSHS = C 4 H 6 S 2 +S 2 HK0 8 . 
(701.) When a sulphovinate is distilled with any salt, as ace- 
tate of lime, a double exchange ensues ; the acetic acid takes 
the place of sulphuric and forms acetic ether, while sulphate 
of lime remains. 

713. Carbovinic Acid. — When carbonic acid acts upon 
a solution of potash in absolute alcohol, crystals of car- 
bovinate of potash are formed ; they have the composition 



ALCOHOL. 371 

C 6 H 5 K0 6 . This acid cannot be isolated. The carbonic 
ether is formed by the action of potassium upon oxalic ether. 
It is a colorless liquid, which contains C 10 H, O 6 , and by the 
action of potash takes up the elements of water, and yields 
alcohol and carbonate of potash. 

By the action of sulphuret of carbon upon an alcoholic 
solution of potash we obtain sulphurized carbovinate of potash, 
in which sulphuret of carbon acts the part of carbonic 
acid. The acid is an oily liquid, of a sour and bitter taste ; 
its formula is CgH^OaSJrricarbovinic acid, CgHcOg, in which 
four equivalents of oxygen are replaced by sulphur. From 
the yellow color of some of its salts it was originally de- 
scribed under the name of xanthic acid. 

Phosphovinic acid is formed by the reaction of one equiva- 
lent of tribasic phosphoric acid and one of alcohol. It is a 
bibasic acid, and in its general characters resembles sulpho- 
vinic acid. Arsenic acid forms an allied compound, the 
arsenovinic acid. 

714. Silicic Ethers. — Two ethereal compounds are formed 
by the reaction of chlorid of silicon upon alcohol. They are 
odorant and volatile liquids, of a pungent taste ; one has the 
formula C, 2 H 15 Si0 6 , and contains the elements of one equiva- 
lent of silicic acid and three of alcohol, minus the elements 
of water. The formula C 4 H 5 Si 2 7 is ascribed to the other, 
and both of them are slowly decomposed by water, and 
rapidly by alkalies into alcohol and silicic acid. When ex- 
posed to moist air in vessels partially closed, they deposit 
silicic acid in beautiful transparent masses, resembling the 
finest rock-crystal. By the action of the chlorid of boron 
upon alcohol, two boracic ethers are produced similar in 
composition and properties to the last : they burn with a fine 
green flame, which is characteristic of the combustion of an 
alcoholic solution of boracic acid — boracic ether being formed 
by this combustion, and in the distillation of alcohol with 
boracic acid. (370.) 

Products of the decomposition of Sulphovinic Acid. 

715. Ether. — When dilute sulphovinic acid is heated to 
boiling, it is decomposed into sulphuric acid and alcohol, but 
when a mixture of equal weights of sulphuric acid and alcohol 
is boiled, water is evolved, and a liquid which may be repre- 
sented as C 4 H 5 0. In the first of these cases, the sulphovinic 
acid takes up the elements of two equivalents of water, and 



372 



ORGANIC CHEMISTRY. 



regenerates alcohol and the acid ; but in the second, this 
acid, when decomposed at the boiling-point of the liquid, 
about 300° F., assumes the elements of but one equivalent of 
water, and evolves the new compound ether. The best pro- 
portions for preparing this ether, are five parts of alcohol of 90 
per cent., and eight of ordinary sulphuric 
acid. The mixture is placed in a flask, 
(a,) through the cork of which is intro- 
duced a thermometer (d) and two tubes, 
one of which (c) conveys away the 
vapors to a condenser, and the other 
(b) is connected with a reservoir of 
alcohol. The mixture is heated to the 
boiling-point (about 300° F.) and care- 
fully maintained at that temperature. 
Alcohol is now admitted through the 
tube b, in a quantity sufficient to pre- 
serve the original level of the liquid in 
the retort, the supply being regulated 
by a stopcock. During the whole ope- 
ration the liquid must be kept violently 
boiling, and the alcohol is then com- 
pletely decomposed into ether and water, 
which distil over together, and condense 
in the receiver. With these precautions 
the process may be carried on for a 
long time, the only limit to it being, 
that the acid is slowly volatilized, in 
combination with a portion of the alcohol. The ether which 
floats on the water in the receiver, is separated, and purified 
by distilling with a little caustic potash. 

This reaction is explained, by the fact that sulphovinic acid 
is formed when the mixture is heated to 285°, and decomposed 
at a temperature a few degrees above it, if the liquid is boiling. 
The alcohol, as it flows into the boiling mixture through 
the tube 6, reduces the temperature at the point of contact, 
so that sulphovinic acid is formed, and a portion of the water 
elininated is immediately volatilized. As soon as the newly 
formed acid mixes with the boiling liquid, it is decomposed 
and ether is evolved. The result is, that with each equiva- 
lent of ether, one of water is volatilized — so that, in effect, 
the alcohol is resolved into these substances. 

This body is the sulphuric ether of commerce, and so 




ALCOHOL. 373 

well known in medicine. But it should be carefully distin- 
guished from those compounds, which like nitric ether, con- 
tain the elements of an acid. 

Ether is a colorless limpid fluid, having the specific gravity 
of *725. It boils at 96°, and evaporates rapidly at ordinary 
temperatures, producing by its evaporation intense cold. Its 
taste and odor are pungent, penetrating, and peculiar. It is 
very combustible, and on account of its volatility should 
never be brought near a flame, as the vapor, when mixed 
with air, is very explosive. The ether of the shops is never 
pure, but contains alcohol, and as it is only sparingly soluble 
in water, may be purified by agitating it with its volume of 
this fluid, which combines with the alcohol, while the ether 
floats on the surface. 

Ether is considerably used as a medicine ; internally as a 
powerful stimulant ; and externally as a refrigerant, from the 
cold produced by its evaporation. 

The inhalation of vapor of ether mingled with atmospheric 
air, produces in the patient a kind of intoxication, which is 
soon followed by a state of stupor, in which the subject is 
insensible to external impressions. It has been lately em- 
ployed under the name of letheon, and with wonderful suc- 
cess, to produce insensibility during surgical operations. 
Pure ether is essential for this purpose, and may be obtained 
by washing the commercial article, as above described. The 
honor of this application — so important in alleviating human 
suffering, — belongs entirely to this country, having been first 
suggested by Dr. Charles S. Jackson, of Boston, and applied 
successfully by Mr. Morton, dentist, of the same city. 

The density of the vapor of ether is 2581, being equal to 
that of two volumes of alcohol vapor, less one of water. 
If we regard four volumes of vapor as representing its 
equivalent, its formula will be C 8 H O 2 , but this formula is 
usually halved, which gives C 4 H 5 0. 

716. Sulphureted Ether, C 4 H 5 S, is a compound obtained 
by the reaction of hydrochloric ether with sulphuret of po- 
tassium, C 4 H 5 C1 + KS=C 4 H 5 S + KC1. It is a colorless vola- 
tile liquid, with an odor resembling that of garlic. Selenium 
and tellurium in like manner replace the oxygen of ether, 
(C 4 H 5 0,) giving us analogous seleniureted and sulphureted 
ethers, (C 4 H 6 Se and C 5 H 5 Te.) 

717. Olefiant Gas, C 4 H 4 . — This product is formed when 
alcohol is mixed with so much sulphuric acid, that the mix- 

32 



374 



ORGANIC CHEMISTRY. 




ture does not boil below 320°. The sulphovinic acid then no 
longer takes up an equivalent of water in its decomposition ; 
but is directly resolved into sulphuric acid and defiant gas, 
C 4 H 6 S 2 8 = S 2 H 2 8 +C 4 H 4 . This is essentially the process 
already described for obtaining this gas, (454,) but a 
more elegant way of preparing it, 
is by an arrangement similar to 
that used for producing ether. Sul- 
phuric acid is diluted with nearly 
one half its weight of water, so 
that its boiling-point is between 320° 
and 330°, and being heated in the 
flask a to ebullition, the vapor of 
boiling alcohol is introduced from 
the flask d by the tube &, which 
dips a little way in the acid. In 
this process, we may suppose that 
sulphovinic acid is formed with the 
escape of two equivalents of water 
in vapor, and is immediately decomposed into sulphuric acid 
and olefiant gas: an equivalent of alcohol yields C 4 H 4 -f 2HO. 
The gas is thus obtained quite pure, and the process may be 
continued for any length of time. 

718. When olefiant gas is mingled with its own volume 
of chlorine, combination ensues, and a heavy oily liquid is 
obtained of a sweet and pungent taste. This compound was 
discovered by an association of Dutch chemists, and is hence 
often called the oil of the Dutch chemists ; its formula is 
C 4 H 4 C1 2 . The action of chlorine gas, aided by the sun's 
rays, will successively replace the hydrogen of this compound. 
The different products are C 4 H 4 C1 2 , C 4 H 3 C1 3 , C 4 H 2 C1 4 , 
C 4 HC1 5 and C 4 C1 6 . A similar series is formed, and in a simi- 
lar manner, from the hydrochloric ether, C 4 H 5 C1. These two 
series of bodies, although represented by the same formulas, 
are quite different in properties, and are interesting examples 
of isomerism. The final product of the action of chlorine 
upon both series of compounds is the chlorid of carbon, 
C 4 H 6 . This is a white crystalline solid of an aromatic odor, 
like camphor ; it melts at 320°, and at a temperature a little 
above this, may be distilled unaltered. It is scarcely com- 
bustible, and is unchanged by acids or alkalies. When its 
vapor is passed through a porcelain tube heated to redness, 
it is resolved into chlorine gas and a new compound, 



ALCOHOL. 375 

C 4 C1 4 , which is a volatile liquid, of the specific gravity of 1-55. 
If the vapor of this compound is passed repeatedly through 
a tube at a bright red heat, it is decomposed into chlorine and 
C 4 C1 2 . This body forms soft, silky crystals, which are vola- 
tile and combustible. 

Products of the Oxydation of Alcohol. 

719. The first effect of oxydizing agents upon alco- 
hol, is to abstract two equivalents of its hydrogen, producing 
a body to which the name of aldehyde has been given.* 
This is produced by the action of nitric acid and various 
other substances, but is best obtained by the following pro- 
cess. Equal weights of powdered bichromate of potash and 
strong alcohol are introduced into a retort, and one and a half 
parts of sulphuric acid are gradually added through the 
tubulure ; a gentle heat is then applied, when a mixture of 
aldehyde and water distils over and may be condensed in a 
cold receiver. The impure product is mixed with ether, and 
saturated with ammonia, when a compound of aldehyde and 
ammonia separates in fine crystals. This, decomposed by 
dilute sulphuric acid, affords pure aldehyde. It is a colorless 
liquid, with a suffocating ethereal odor ,- has a specific gravity 
of -790, and boils at 70° F. Its formula is C 4 H 4 2 = alco- 
hol C 4 H 6 2 — Ha ; a solution of potash decomposes aldehyde, 
and forms a brown resinous substance, which is named 
aldehyde resin : this reaction enables us to detect the presence 
of aldehyde in liquids. 

When a solution of aldehyde, mixed with a little ammo- 
nia, is added to a dilute solution of nitrate of silver, and the 
mixture is heated : the silver is reduced, and lines the vessel 
with a brilliant metallic film which forms a perfect mirror. 
This fact has been successfully applied in the manufacture of 
mirrors. 

720. Aldehyde cannot be preserved unchanged, even in 
sealed tubes, but is slowly changed into two polymeric com- 
pounds. One of these, elaldehyde, is a dense oily fluid, 
which has none of the properties of aldehyde. The den- 
sity of its vapor is three times that of aldehyde ; and its 
formula is 3C 4 H 4 2 = C^H^Og. The other body, metaldehyde, 
forms hard white prisms ; it is formed by the union of four 

* From alcohol de hydrogenatus. 



376 



ORGANIC CHEMISTRY. 



equivalents of aldehyde, and has the composition Ci 6 H 16 8 . 
When aldehyde is exposed to the air, it gradually absorbs 
oxygen, and is converted into acetic acid. 

Acetic Acid, C 4 H 4 4 . — This is the acid of vinegar ; and it 
is produced by the oxydation of alcohol, or aldehyde. The 
latter body combines directly with two equivalents of oxygen, 
C 4 H 4 2 + 2 =C 4 H 4 4 . When alcohol is heated with a mix- 
ture of hydrate of potash and lime, hydrogen gas is evolved 
and acetate of potash is formed. The reaction is thus ex- 
plained : C 4 H 6 2 + KH0 2 = C 4 H 3 K0 4 + 4H. 

721 . Pure alcohol undergoes no change when exposed to 
the air alone ; but if its vapor mixed with air is brought into 
contact with platinum-black, it slowly unites with oxygen to 
form aldehyde, which readily absorbs another portion of oxy- 
gen, and produces acetic acid. The oxydating power of finely 
divided platinum has been before alluded to : it absorbs or 
condenses great quantities of gases and vapors in its pores, 
where they appear to be brought together in such a state that 
they readily react upon each other. 

722. The formation of acetic acid may be beautifully 
shown by placing a little platinum-black in a watch-glass, by 
the side of a small vessel of alcohol, covering the whole 
with a bell-glass, and setting it in the sun-light. In a short 
time the vapor of acetic acid will condense on the sides of 
the glass, and run down in drops ; and if we occasionally 
admit fresh air by raising the bell-jar, the whole of the alco- 
hol will be acidified in a few hours. 

The change consists in the loss of two equivalents of hy- 
drogen, and the addition of two of oxygen. 

In the ordinary process for vinegar, alcoholic liquors, as 
wine and cider, are exposed to the air in open vessels. Although 
a mixture of pure alcohol and water does not absorb oxygen 
from the air, a small portion of any ferment, as vinegar 
already formed, or the substance called 
mother of vinegar, enables it to combine with 
oxygen. In this process, the essential thing 
is a free supply of air, and a proper temper- 
ature. In the manufacture of vinegar on the 
large scale, this is secured by causing the 
liquor (b) to trickle from threads of cotton 
drawn through holes, over shavings of beech- 
wood previously soaked in vinegar, and con- 
tained in a large cask with holes in its sides, (c c c c,) so as 




ALCOHOL. 377 

to admit a free circulation of air. In this way a vast surface 
is exposed, and the absorption of oxygen is very rapid, 
causing an elevation of 20° or 30° in the temperature. The 
liquid is passed through this apparatus four or five times in 
the course of twenty-four hours, in which time the change 
of the alcohol into vinegar is generally complete. The pro- 
duct is collected in the vessel a. 

723. Acetic acid is also obtained by distilling wood in 
close vessels ; the volatile ingredients are expelled and char- 
coal alone remains ; the products are, besides carbonic acid 
and carbureted hydrogen, a large quantity of acetic acid, 
mixed with oily and tarry matters, from which it is separated 
mechanically. The acid thus prepared is known as pyrolig- 
neous acid, and is largely used in the arts of dyeing and 
calico-printing, but being contaminated by empyreumatic 
oils, is not fit for the purposes of domestic economy. By 
combining it with bases, salts are obtained, which, when de- 
composed, afford a pure acid. 

724. By distilling dried acetate of soda with strong sul- 
phuric acid, a very concentrated acid is obtained, which, 
when exposed to cold, deposits crystals of pure acetic acid, 
C 4 H 4 4 . The pure acid is solid below 60° F. ; when liquid 
it has a specific gravity of 1*063, and boils at 248°. It is 
perfectly soluble in water, alcohol, and ether ; it has a pun- 
gent fragrant odor and a very acid taste, and when applied 
to the skin is highly corrosive. The acid is monobasic ; all 
its salts are soluble in water. 

Acetates. 

725. Acetate of Potash (C 4 H 3 K0 4 ), is easily prepared by 
neutralizing acetic acid with carbonate of potash. It is a 
very soluble deliquescent salt, and is employed in medicine. 
Acetate of soda (C 4 H 3 Na0 4 ), forms large crystals with six 
equivalents of water. It is prepared in large quantities from 
pyroligneous acid. The salt is healed to destroy the oily 
matter, and then affords by its decomposition a pure acid. 
Acetate of ammonia (C 4 H 4 4 +NH 3 ), is used in medicine by 
the name of the spirit of Mindereus. It is prepared by 
saturating acetic acid with ammonia, and is exceedingly 
soluble and volatile. The acetate of zinc is a beautiful white 
salt, and is employed as a tonic and astringent. The acetate 
of alumina is much used in dyeing ; it is obtained by decom- 



378 ORGANIC CHEMISTRY. 

posing a solution of alum by one of acetate of lead ; sulphate 
of lead precipitates, and acetate of alumina with acetate of 
potasn remains in solution. The acetate and sesqui- acetate 
of iron are prepared in a similar manner, and are largely- 
employed in calico-printing and dyeing. The constitution of 
the sesqui-acetates has been already explained (676). 

726. Acetate of Lead, C 4 H 3 Pb,0 4 . — This salt is well 
known under the name of sugar of lead. It is prepared by 
dissolving oxyd of lead (litharge) in acetic acid, and crystal- 
lizes with three equivalents of water, which are expelled by 
gentle heat. It is a white salt, with a very sweet and astrin- 
gent taste, and is often employed as a medicine ; but is poi- 
sonous, and should be used internally with caution. 

The acetate of lead has a great tendency to combine with 
oxyd of lead, with which it forms several definite compounds. 
These are generally designated as basic salts, but should be 
carefully distinguished from the salts containing more than 
one equivalent of base, which are formed by bibasic and 
tribasic acids. In these last, the metal replaces the hydrogen 
of the acid, but in the basic acetates, the neutral salt combines 
directly with the oxyd. To distinguish them, the term sur- 
basic is applied, and the compound of the acetate with two 
equivalents of oxyd of lead is called the bi-surbasic acetate 
of lead. Three of these compounds are known, in which 
the acetate is combined with one-half, two, and five equivalents 
of oxyd. The second is the only one of importance. 

727. Bi-surbasic Acetate of Lead, C 4 H 3 Pb0 4 -|-2PbO. — 
This salt, commonly called the tribasic acetate, is obtained 
by digesting a solution of six parts of the acetate with seven 
of litharge: the oxyd is dissolved, and the liquid affords, by 
evaporation, a salt crystallizing in long needles. It is also 
slowly formed when metallic lead is digested in an open vessel 
with a solution of the acetate, oxygen being absorbed from 
the air. The salt is very soluble in water, and its solution 
has an alkaline reaction : it is well known in pharmacy as 
Goulard's Extract, or solution of lead. When exposed to 
the air, it absorbs carbonic acid, and the two equivalents of 
oxyd of lead are precipitated as a carbonate. This reaction 
enables us to explain the formation of white lead, (606.) 

728. A process frequently employed is to mix litharge and 
about T £o-th of sugar of lead into a thin paste with water ; 
the mixture is gently heated, and a current of carbonic acid 
is passed through it. The acetate of lead dissolves a portion 



ALCOHOL. 379 

of the oxyd to form the tribasic salt; this is immediately 
decomposed by the carbonic acid, which precipitates carbonate 
of lead, and leaves the acetate free to dissolve a new portion 
of oxyd. In this way the smallest quantity of the acetate is 
able to convert a large portion of the oxyd into carbonate, 
and at the end of the process to remain unaltered. 

729. In the ordinary process, the plates of lead are ex 
posed to the action of acetic acid, moisture, air, and carbonic 
acid from the fermenting tan. The lead immediately be 
comes covered with a film of oxyd by the action of the air. 
This is dissolved by the vapor of acetic acid, and forms a 
solution of neutral acetate, which moistens the plates and 
gradually acts upon them, forming by the aid of the atmo- 
spheric oxygen, the basic acetate. This is decomposed by 
the carbonic acid, in the same manner as in the last process, 
and the neutral acetate is again set free to act upon the me- 
tallic lead ; the process goes on until all the lead is carbonated. 
In this way a small quantity of acetic acid will, under favor- 
able circumstances, convert a hundred times its weight of 
lead into carbonate in a few weeks. 

730. Acetate of Copper, C 4 H 3 Cu0 4 . — This salt is quite 
soluble, and forms beautiful green crystals of the monoclinate 
system, containing one equivalent of water. The acetate of 
copper forms several surbasic salts which are insoluble in water. 
The fine green pigment called verdigris is a mixture of two 
or more of these ; all of these copper salts are very poisonous. 

The Acetate of Silver (C 4 H 3 Ag0 4 ), crystallizes in white 
scales, and is the least soluble of the acetates. 

731. Chloracetic Acid, C 4 C1 3 H0 4 . — When acetic acid is 
placed in a vessel of chlorine gas, and exposed to the sun- 
light, three equivalents of its hydrogen are removed in the 
form of hydrochloric acid, and three of chlorine substituted 
in their place. The chloracetic acid closely resembles tne 
acetic, and its salts correspond to the acetates of the same 
bases. A solution of any chloracetate is decomposed by an 
amalgam of potassium : the chlorine is removed, and we 
obtain chlorid of potassium and ordinary acetate of potash. 

732. Acetic Ether, C 8 H 8 4 . — This is formed by the 
direct action of acetic acid on alcohol ; but is best obtained 
by distilling five parts of acetate of soda, eight of sulphuric 
acid, and three of alcohol. It is a very fragrant volatile 
liquid ; the odor of vinegar formed from fermented liquor is 
due to a little acetic ether. It contains the elements of one 



380 ORGANIC CHEMISTRY. 

equivalent of alcohol, and one of acetic acid, less two o* 
water, C 4 H 6 2 + C 4 H 4 4 =C 8 H 8 4 +2HO. 

733. When acetic acid or acetates are decomposed by 
heat, a volatile liquid called acetone is obtained : it is derived 
from the elements of two equivalents of acetic acid, by the 
abstraction of two of carbonic acid gas and two of water, 
2(C 4 H 4 4 )-(2C0 2 +2HO)=C 6 H 6 2 . The vapor of acetic 
acid, when passed through an ignited tube, is completely 
resolved into these substances. Acetone is a very volatile 
liquid, of specific gravity *793, and has a pungent and peculiar 
odor. It is readily soluble in water, alcohol and ether. 
When distilled with a mixture of chromate of potash and 
sulphuric acid, it yields acetic acid. 

By the action of an excess of potash upon an acetate, it is 
decomposed into carbonic acid and marsh gas, C 4 H 4 4 = 
2C0 2 +C 2 H 4 , (451.) 

WOOD-SPIRIT, C 2 H 4 2 . 

734. This substance is a product of the destructive dis- 
tillation of wood : when the crude pyroligneous acid (723) 
is saturated by lime and distilled, impure wood-spirit is 
obtained, and may be afterwards purified by repeated dis- 
tillations. It is a colorless liquid, of a peculiar and some- 
what unpleasant odor, and a hot pungent taste. It has a 
specific gravity of *798, and boils at 152°; it is very com- 
bustible, and burns with a pale blue flame. Like alcohol, it 
mixes in all proportions with water. It is occasionally used 
in the arts for dissolving resins, and making varnishes ; and 
the pure wood-spirit has lately acquired some celebrity in 
the treatment of phthisis, under the name of wood-naphtha. 

This substance is known in commerce as pyroxylic 
spirit ;* from its resemblance to alcohol, it has been called 
methylic alcohol,* and the name of methol is also employed. 

Wood-spirit is closely affined to alcohol in all its chemical 
relations. By the action of acids it gives rise to ethers, 
which in their properties and mode of formation are so 
similar to the corresponding bodies from alcohol, that what 
has been said of these will apply to them in every respect. 
W T ith bibasic acids it forms methylic acids similar to the 
vinic. 

* Pyroxylic spirit, from pur, fire, and hulon, wood, in allusion to 
its origin ; and methylic alcohol, from methu, wine, and htdoji : the 
wine or alcohol of wood. 



WOOD-SPIRIT. 381 

735. The Nitric Methylic Ether, C 2 H 3 N0 6 , is formed by 
distilling wood-spirit with nitre and sulphuric acid. It is a 
heavy oily fluid, which by the action of a solution of potash 
takes up the elements of two equivalents of water, and yields 
nitrate of potash and wood-spirit. Its vapor, when heated to 
250°, explodes with great violence. 

Hydrochloric Methylic Ether, C 2 H 3 C1, is obtained in the 
form of a gas, having a sweet ethereal taste, and a specific 
gravity of 1*731. The compounds containing bromine and 
iodine are liquids. 

736. Sulphuric Methylic Ether. — This compound, the 
analogue of which is unknown in the alcohol series, is 
obtained by distilling wood-spirit with eight or ten parts of 
sulphuric acid. It is a tasteless, oily fluid, which has an allia- 
ceous odor ; boils at 370°, and has a specific gravity of 1-324. 
It is formed from an equivalent of sulphuric acid and two 
of wood-spirit, by the loss of four of water, S 2 H 2 8 + 2C 2 H 4 
2 =C 4 H 6 S 2 8 -f 4HO. By the action of boiling water it takes 
the elements of two equivalents of that liquid, and is in part 
decomposed, yielding wood-spirit and sulphomcthylic acid, 
and by excess of caustic potash the decomposition is com- 
plete. By the action of ammonia a white crystalline com- 
pound is formed,* which is called sulphamcth ylane ; one 
equivalent of the ether and one of ammonia, yield one 
equivalent of the new substance and one of wood-spirit, 
C 4 H 6 S 2 8 + NH 3 =C 2 H 5 NS 2 6 + C 2 H 4 2 . Its nature will be 
understood by referring to what we have said of the simi- 
larity between the ethers and amides, (705.) We have 
represented the former as derived from alcohol and an acid, 
by the loss of two equivalents of water ; and the amides, in 
the same manner, are formed from ammonia and an acid. 
Sulphamethylane is an ether- amide, and is formed from one 
equivalent of ammonia and one of wood-spirit, with one of 
a bibasic acid, by the separation of four of water ; it therefore 
corresponds to the neutral sulphuric methylic ether, and like 
it is decomposed by potash, taking up the elements of four 
equivalents of water, and yielding sulphuric acid, wood-spirit, 
and ammonia. 

737. Sulphomethylic Acid, C 2 H-S 2 8 . — This acid is ob- 
tained, by a similar process to that for the sulphovinic, and 
like it is a monobasic acid, forming soluble salts with lime and 
baryta. It is, however, more permanent than the sulpho- 
vinic acid, and may be obtained in small crystals which are 
very soluble in water. 



382 ORGANIC CHEMISTRY. 

738. When sulphomethylic acid is decomposed by heat, 
it undergoes a change similar to the sulphovinic acid, and 
evolves a colorless gas, which is wood-spirit, minus the ele- 
ments of one equivalent of water, C 2 H 4 2 — HO = C 2 H 3 0. — 
This corresponds precisely to the ether of alcohol, and is called 
wood ether, methylic ether or mether : it is not condensed 
by intense cold ; has a pungent taste and odor, and is soluble 
in water and alcohol. 

739. In the same manner as hydrochloric ether may be 
considered as derived from acetene, which is alcohol minus 
two equivalents of oxygen, the corresponding compounds of 
wood-spirit may be derived from marsh gas, which is C 2 H 4 2 — 
2 =C 2 H 4 . The name of formene is hence given to this gas. 
Several compounds formed from the action of chlorine and 
its congeners upon bodies of the alcohol and wood-spirit 
series, may be viewed as formene, in which a part of the 
hydrogen is replaced by chlorine, bromine, or iodine. 

Chloroform ; Tri-chlorinized Formene, C 2 HC1 3 . — This is 
formed when alcohol or wood-spirit is distilled with a solu- 
tion of two or three parts of chlorid of lime, in twenty parts 
of water. It is a heavy oily liquid, nearly insoluble in 
water, which boils at 141°, and has a specific gravity of 1-48. 
It has a very sweet and pungent taste, and its alcoholic solu- 
tion is employed in medicine under the name of chloric 
ether. Bromine forms a similar compound. 

Iodiform ; Tri-iodized Formene, C 2 HI 3 , is obtained when 
iodine acts upon an alcoholic solution of potash. It crystal- 
lizes in bright yellow scales, and has a pungent aromatic 
taste. All of these compounds are decomposed by an alco- 
holic solution of hydrate of potash, affording a compound of 
the salt-radical with potassium, and formate of potash, 
C 2 HC1 3 + 4KO= 3KC1+ C 2 HK0 4 . 

When chloroform is exposed to the action of chlorine gas, 
aided by the sun's light, the remaining equivalent of hydro- 
gen is removed and a chlorid of carbon is obtained, C 2 C1 4 , or 
perchlorinized formene. 

Oxydation of Wood- Spirit. 

740. When the vapor of wood-spirit mixed with air is 
exposed to the action of platinum-black, it loses hydrogen 
and absorbs oxygen, producing water and formic acid. This 
is derived from wood-spirit by a reaction exactly similar to 
that producing acetic acid from alcohol ; two equivalents of 



WOOD-SPIRIT. 383 

hydrogen combine with oxygen to form water, and two of 
oxygen unite with the residue, (C 2 H 4 2 — H 2 ) + 2 =C 2 H 2 4 . 
The intermediate product of this reaction, corresponding to 
aldehyde, has not been obtained. When wood-spirit is heated 
with a mixture of hydrate of potash and lime, hydrogen gas 
is evolved, and formate of potash is produced. 

741. Formic acid occurs as a secretion of the red-ant, 
(Formica rufa,) from whence it derives its name, and may 
be obtained by distilling the ants with water. It is also a 
product of the oxydation of sugar, and many other organic 
substances, and is best prepared by the following process. 
800 grains of bichromate of potash and 300 of sugar, are 
dissolved in seven ounces of water. The mixture is placed 
in a retort, and one measured ounce of sulphuric acid very 
gradually added ; it is then distilled with a gentle heat, until 
three ounces of liquid are obtained. This is dilute formic 
acid, and may be used to form salts, which when decom- 
posed afford a strong acid. 

The pure acid is obtained by passing sulphureted hydrogen 
gas over dry formate of lead ; sulphuret of lead and formic 
acid are produced. The action is aided by a gentle heat, 
and the acid distils over. It is a colorless liquid, of 
specific gravity 1-235, which boils at 212°, and at 32° crys- 
tallizes, like acetic acid, in shining plates. It fumes in the 
air, and has a very pungent odor, resembling that of ants ; it 
is powerfully acid and very corrosive, instantly blistering the 
skin. When this acid or its salts are heated with strong 
sulphuric acid, it is decomposed with the evolution of pure 
carbonic oxyd gas, C 2 H 2 4 =2CO-f 2HO. When formic 
acid or a formate is heated with solutions of the noble metals, 
it reduces them, and is itself decomposed with the evolution 
of carbonic acid gas. 

The formates closely resemble the acetates. The formate 
of potash, C 2 HK0 4 , is very soluble. The formate of silver, 
C 2 HAg0 4 , crystallizes in scales ; when its solution is boiled, 
the silver is precipitated in the metallic state, while carbonic 
acid and carbonic oxyd gases escape, C 2 HAg0 4 =Ag-f HO + 
C0 2 + CO. 

AMYLIC ALCOHOL, CjoH^Oj. 

742. In the distillation of spirit made from potatoes, the 
last portions of the liquid are rendered milky by a peculiar 
~;i„ «uhstance which separates on standing, and to which the 



384) ORGANIC CHEMISTRY. 

name of potato oil, or fusel oil, is given. It does not exist in 
the vegetable, but is a product of the fermentation, and is 
also found in the spirit obtained from the fermentation of 
raisins and the juice of beets. It is freed from alcohol by 
agitation with water, and is afterwards purified by distillation. 
When pure it is a colorless liquid, which is insoluble in water, 
has a specific gravity of -818, and boils at 269°. It has a 
burning taste, and a pungent disagreeable odor, which excites 
coughing, and often distressing nausea. 

It closely resembles alcohol and wood-spirit in its chemical 
relations, and has hence received the name of amylic alcohol* 
or amylol. By the action of acids it yields ethers, which are 
similar to those derived from alcohol. 

743. The Acetic Amylic Ether (C 14 H 14 4 ), is obtained by 
distilling potato oil with a mixture of acetate of potash and 
sulphuric acid. One equivalent of amylic alcohol, and one 
of acetic acid, yield one of* the ether, and two of water; 
C lc H 12 2 + C 4 H 4 4 =C 14 H 14 4 + 2HO. It is a colorless fra- 
grant liquid, which is decomposed by an alcoholic solution of 
potash, forming acetate of potash and potato oil. 

Hydrochloric Amylic Ether (C 10 H n Cl), is formed when 
potato oil is distilled with hydrochloric acid. It may be 
viewed as a substitution product of valerene (C 10 H 12 ), a body 
corresponding to acetene. By the action of nitric acid upon 
potato oil, a liquid is obtained corresponding to the hypo- 
nitrous ether from alcohol, which may be considered as nitric 
valerene. 

744. With sulphuric acid, amylic alcohol forms a coupled 
acid which is quite similar to the sulphovinic, and is called 
sulphamylic acid. It is derived from one equivalent of sul- 
phuric acid and one of the amylic alcohol, by the abstraction 
of the elements of water ; and by the action of alkalies is 
decomposed with the regeneration of the potato oil and the 
formation of a sulphate. 

745. The Amylic Ether or Amylether (C, H n O), has been 
obtained, but its characters have not been studied. It appears 
to be formed by the distillation of sulphamylic acid. 

When potato oil is distilled with an excess of sulphuric 
acid, a volatile oily liquid is obtained, which is formed from 
the amylic alcohol by the abstraction of the elements of two 

* From amylum, starch, as it was supposed to be derived from 
the fermentation of the starch of the potatoes. 



AMYLIC ALCOHOL. 385 

equivalents of water. It is called paramilene, and has the 
formula C 10 H 10 =C 10 H 12 O 2 — 2 HO: it corresponds precisely to 
olefiant gas in the alcohol series. 

Oxydation of Amylic Alcohol or Potato Oil. 

746. When this substance is exposed to the air, it slowly 
absorbs oxygen, and becomes acid : the change is effected 
much more rapidly when the oil is dropped upon platinum- 
black. The product of this oxydation is valerianic acid 
(C, Hj O 4 ) : it is formed by a process similar to that yielding 
acetic acid. An equivalent of the oil loses two of hydrogen, 
which combine with oxygen, producing water, and the residue 
takes two of oxygen to form the acid, C, H I2 O 2 +4O= 
C, H, O 4 + 2HO. The acid is also formed with disengage- 
ment of hydrogen gas, when the oil is heated with hydrate 
of potash ; valerianate of potash is obtained, which is de- 
composed by distilling with dilute sulphuric acid. This acid 
is identical with that which exists in the Valeriana offi- 
cinalis, and is obtained by distilling the root of that plant 
with water. It is to this acid that the valerian owes its 
medicinal properties. Valerianic acid has been found in a 
free state in cheese, and it is to its presence that the flavor of 
old cheese is in part due. 

747. Valerianic acid is a colorless oily fluid, which boils at 
347°, and has a specific gravity of *937. Its taste is sharp 
and acid, and its odor powerful and disagreeable, resembling 
that of valerian. Water dissolves a large quantity of it, and 
it is readily soluble in alcohol. Like the acetic and formic 
acids, it is monobasic : its salts are all soluble in water, and 
have a slight odor of valerian. The valerianate of potash 
is very soluble and deliquescent ; that of baryta (CuHjBaC},), 
crystallizes in fine transparent prisms. The valerianate of 
zinc (C, H 9 ZnO 4 ), is prepared by neutralizing the acid with 
carbonate of zinc, and crystallizes in white scales. It is em- 
ployed in medicine as a substitute for valerian, the peculiar 
medicinal powers of which it possesses in a high degree. 

By the action of chlorine upon this acid, a portion of its 
hydrogen is replaced, and trichlorinized valerianic acid 
is formed, which corresponds to the chloracetic acid. 

ETHAL, C 32 U^0 2 . 

748. This substance is obtained by the action of the 
hydrate of potash upon spermaceti : it is a white crystalline 

33 



386 ORGANIC CHEMISTRY. 

solid, which fuses at 118° : is insoluble in water, but soluble 
in alcohol, and may be volatilized without decomposition. 
In its chemical characters it is closely related to alcohol : 
by the action of perchlorid of phosphorus, it yields a com- 
pound which corresponds precisely to the hydrochloric ether 
from alcohol : it has the composition G^EL^Cl. Ethal, when 
heated with sulphuric acid, combines with it to form a 
coupled acid, which is called the sulphocetic or sulphethalic : 
it is monobasic, and is formed precisely like the sulphovinic 
from one equivalent of sulphuric acid and one of ethal, by 
the abstraction of two of water. When ethal is distilled with 
anhydrous phosphoric acid, it loses the elements of two 
equivalents of water, and yields a carbo-hydrogen, C 32 H32, 
which is called cetene, and is polymeric of olefiant gas. 

749. The substance known as spermaceti or cetene, may 
be regarded as the aldehyde of ethal. It is found in immense 
cavities in the head of the sperm whale, where it is mixed 
with a portion of oil. The fluid parts are removed by 
pressure, and the remaining oil dissolved by washing in a 
dilute solution of potash. Pure spermaceti fuses at 120°, 
and forms in cooling radiated masses of beautiful crystalline 
plates with a pearly lustre. It is insoluble in water, but 
soluble in strong alcohol and ether. Its formula is C^H^C^, 
equal to ethal minus two equivalents of hydrogen. When 
fused with a gentle heat and mixed with hydrate of potash, 
it is decomposed, yielding ethal and the potash salt of ethalic 
acid, 20^^02 + KO,HO= Ca^sA + C s2 H 31 K0 4 . 

750. When ethal is heated with hydrate of potash to 
about 400°, hydrogen gas is evolved, and ethalic acid 
is formed. The reaction is similar to that producing acetic 
acid from alcohol, (CgaH^Oa— H 2 ) + 02=032113204. This is 
also obtained when a mixture of spermaceti and potash is 
heated to the same temperature : the aldehyde in this case 
simply takes two equivalents of oxygen to form the acid. 

The ethalic acid is a white solid, lighter than water ; it 
fuses at 131°, and forms on cooling a brilliant radiated 
crystalline mass ; it is soluble in alcohol, but insoluble in 
water. This acid is monobasic : the ethalates with an 
alkaline base are soluble ; the others are insoluble in water. 
Ethalic acid belongs to a class of fatty acids yet to be 
described, and its character and relations will be again 
alluded to. 



RELATIONS OF THE PRECEDING BODIES. 387 

On the Relations of the preceding Bodies. 

751. The four classes of compounds last described have 
been shown to be nearly affined in their chemical characters : 
they may be viewed as members of a group of which 
common alcohol or spirits of wine is the representative, and 
may be designated by the common name of alcohols. They 
unite with sulphuric acid, with separation of the elements of 
water, to form coupled acids — yield ethers by the action of 
other acids ; aldehydes by the abstraction of two equivalents 
of hydrogen ; monobasic acids which have the composition 
of the aldehydes plus two equivalents of oxygen, and hydro- 
carbons which correspond to the alcohols, minus two 
equivalents of water. Although the whole of these charac- 
teristics are not developed in any one of the group, they 
agree in a sufficient number to establish their close affinities. 
These relations, which depend upon similarity of constitution, 
are designated as homologous, and the alcohols are called 
homologues, or homologous bodies. This relation is to 
be carefully distinguished from analogy, which refers to 
external or accidental resemblance. To illustrate this by an 
example — alcohol resembles acetone in being volatile, very 
combustible, and soluble in water, and ethal is like sperma- 
ceti in being solid, crystalline, and insoluble ; but these 
external resemblances are only analogies, and if we examine 
the constitution of the bodies, we shall find that the volatile, 
soluble alcohol, and the solid, crystalline ethal, are the 
bodies which are really affined to each other. 

752. In the alcohols the oxygen is always equal to two 
equivalents, and the proportion of hydrogen is greater, than 
that of the carbon by two; so that in effect their decom- 
position affords two equivalents of water, and a compound 
of equal equivalents of carbon and hydrogen. The acids 
derived from them all contain four of oxygen, and equal 
equivalents of the other elements. 

Wood-spirit, C2H4O2 Formic acid, C2H2O4 

Alcohol, C 4 H 6 2 Acetic " C 4 H 4 4 

Potato oil, C10H12O2 Valerianic acid, C10H10O4 

Ethal, 032^02 Ethalic « C32H320 4 

From these and many other instances we arrive at the 
important law that in a class of homologous bodies the pro- 
portion of oxygen is invariably the same ; and that the equi- 
valents of carbon and hydrogen bear a similar proportion to 



388 ORGANIC CHEM1STKY. 

each other, being either equal, or varying by a common 
difference. The amount of nitrogen, when this element is 
present in homologues, is like the oxygen invariable: and 
when chlorine replaces hydrogen, it is subject to the same law 
as hydrogen itself; the like is true of sulphur replacing 
oxygen. 

BITTER ALMOND OIL, C M H 6 02. 

753. Benzoilol, Essential Oil of Bitter Almonds. — This 
oil does not exist ready formed in the almonds, but is pro- 
duced by the reaction of certain principles contained in the 
kernel when aided by the presence of water. It is obtained 
by bruising bitter almonds into a paste with water, and dis- 
tilling the mixture, when the oil passes over, with hydro- 
cyanic acid and other impurities. It is purified by redistilling 
it from a mixture of protochlorid of iron and lime. It is a 
colorless oily liquid, of a pungent burning taste, and very 
fragrant odor, like that of bruised bitter almonds. It boils at 
356°, but its vapor distils over with that of water at 212°; 
its specific gravity is 1*073. It is often used in flavoring 
articles of food, but the crude oil which is sold for this pur- 
pose is exceedingly poisonous : from the experiments of 
Pereira it appears that the pure oil is harmless. 

Sulphureted Benzoilol. — By the action of hydro-sul- 
phuret of ammonia upon bitter almond oil, its oxygen is re- 
placed by sulphur, and an insoluble powder is obtained of 
the formula Ci 4 H 6 S 2 . Its decomposition by heat gives rise to 
a variety of new and curious products. 

754. Chlorinized Benzoilol, C 14 H 5 C10 2 . — This is obtained 
by the action of dry chlorine gas upon the oil of bitter 
almonds. It is a colorless liquid, which is decomposed by 
alkalies, yielding a chlorid and a benzoate. By distilling this 
with bromid or iodid of potassium, similar compounds are 
obtained, in which bromine or iodine replaces an equivalent 
of hydrogen. 

The action of dry ammonia upon the chlorinized benzoilol 
yields hydrochloric acid, and a new substance, benzamide, 
C M H 5 C10 2 + NH3=C 14 H7N0 2 +HC1. It is soluble in water, 
and crystallizes in beautiful prisms. It contains the elements 
of benzoate of ammonia minus two equivalents of water, 
and by the action of alkalies or acids takes up the elements 
of water and regenerates benzoic acid and ammonia, (697.) 



BITTER ALMOND OIL. 389 

Hydrobenzamide. — "When bitter almond oil is placed in a 
concentrated solution of ammonia, it is gradually converted 
into a white crystalline mass of this substance. It is formed 
from three equivalents of benzoilol and two of ammonia by 
the abstraction of the elements of six equivalents of water, 
3(C I4 H60 2 ) + 2NH 3 =C 42 H 18 N2+6HO. In this reaction the 
ammonia loses the whole of its hydrogen, which unites with 
the oxygen of the oil, and the residue (N 2 ) is substituted for 
6 . By the action of hydrochloric acid it takes up the ele- 
ments of water and regenerates the oil and ammonia ; the 
latter combines with the acid to form sal ammoniac. When 
boiled in a solution of potash it is converted into a metameric 
modification, which is no longer decomposed by acids, but 
unites directly with them, and neutralizes them. This sub- 
stance, which is an alkaloid, is also formed when ammonia 
is passed through an alcoholic solution of the oil of bitter 
almonds : it is called benzoline or amarine. 

755. When bitter almond oil is exposed to the air, it rapidly 
absorbs oxygen, and is converted into a white crystalline 
substance, which is benzoic acid : this is formed by the com- 
bination of two equivalents of oxygen. The same effect is 
produced when the oil is heated with hydrate of potash : 
hydrogen gas is evolved, and benzoale of potash formed. A 
more abundant source of benzoic acid is found in benzoin, a 
fragrant resinous substance which is obtained from the Laurus 
benzoin. This contains a large quantity of the acid, which 
may be procured by exposure to a gentle heat, when the acid 
is volatilized, and condenses as a white sublimate. It is also 
obtained by boiling the benzoin with lime, which forms ben- 
zoate of lime ; hydrochloric acid added to the previously 
concentrated solution, precipitates the pure acid in crystalline 
plates. Benzoic acid forms light silky crystals of a pearly 
whiteness, and has a pleasant aromatic taste, very slightly 
acid. When pure it is inodorous, but generally has a little 
volatile oil adhering to it, which gives it a fragrant odor, like 
vanilla. It is volatile at a gentle heat, evolving a suffocating 
vapor, which condenses unchanged. It is very slightly soluble 
in cold, but more easily in hot water. 

The formula of benzoic acid is C^H^ ; it is monobasic, 
and forms a large class of salts, which are of but little im- 
portance. 

When it is boiled for some time with strong nitric acid, 
nitrobenzoic acid is obtained. One equivalent of benzoic 
33* 



390 ORGANIC CHEMISTE.Y. 

acid and one of nitric acid lose the elements of two equiva- 
lents of water, and the residues unite. The new acid is 
monobasic, and resembles the benzoic in its properties. 

756. Benzoine. — When the crude oil of bitter almonds 
is mixed with an alcoholic solution of potash, it is gradually- 
converted into a white crystalline substance, which is called 
benzoine. It is polymeric of the oil, and is formed by the 
union of two equivalents of it ; its formula is consequently 
C2 8 H 12 4 . When the vapor of benzoine is passed through a 
red-hot tube, it is reconverted into bitter almond oil. 

757. Benzene. — The vapor of benzoic acid passed through 
a red-hot gun-barrel, is decomposed into carbonic acid and a 
new substance named benzene or benzole, which is C 12 H 6 
C 14 H 6 4 =2C0 2 + C 12 H 6 . — Benzene is more easily obtained by 
distilling benzoic acid with slaked lime, which combines with 
the carbonic acid. It is a colorless, fragrant liquid, which 
boils at 187°, and has a specific gravity of -830. Benzene is 
formed when the fat oils are decomposed at a red heat, and is 
obtained in the manufacture of oil-gas for illumination. 

With fuming sulphuric acid, benzene yields a coupled acid, 
which is monobasic, and a neutral compound, sulphobenzide, 
containing the elements of two equivalents of benzene, and 
one of sulphuric acid, minus two of water. The action of 
nitric acid produces a dense oily liquid of a very sweet taste; 
it is nitrobenzene, C, 2 H 4 N0 4 , and is derived from one equiva- 
lent of benzene and one of nitric acid, by the abstraction of 
two equivalents of water. We may suppose that two equiv- 
alents of hydrogen in the benzene unite with two of oxygen 
from the acid, C 12 H 6 — H 2 = C^H, and NH0 6 — 2 = NH0 4 . 
The residue of the acid is then substituted for the two equiv- 
alents of hydrogen in the benzene, thus, C, 2 H 4 NH0 4 . 

By the further action of fuming nitric acid, a crystalline 
compound, named binitrobenzene, is obtained. It is derived 
in the same manner as the last, by the action of another 
equivalent of the acid, and has the formula CjaHJNaOg. 

OIL OF CUMIN. 

758. The essential oil of the seeds of cumin, (Cvminum 
cyminum,) has the formula C^H^C^, and when heated with 
hydrate of potash, is oxydized with the evolution of hydrogen, 
forming cuminate of potash. The cuminic acid, C^H^O^ is 
white and crystalline, resembling the benzoic. Cuminol and 



OIL OF SPIREA ULMARIA. 391 

cuminic acid are homologues of benzoilol and the benzoic 
acid. The acids in both instances are formed by fixing 2 . 
and contain four equivalents of oxygen. It will be seen that 
in these oils the difference between the proportion of carbon 
and hydrogen is the same, and equals eight equivalents. 

OIL OP SPIREA ULMARIA, C u H € 4 . 

759. Salicylol. — This is obtained when the flowers of the 
Spirea ulmaria, (pride of the meadow,) are distilled with 
water; and is artificially formed by the oxydation of salicine, 
a process which will be described under that substance. 
Salicylol is a colorless fluid, of fragrant odor, like the flower 
of the spirea, and has a pungent taste. It has a specific 
gravity of 1*173, and boils at 380°. By the action of metal- 
lic oxyds it yields compounds, in which an equivalent of 
hydrogen is replaced by a metal ; but in its other relations it 
does not resemble an acid. It does not pre-exist in the plant 
from which it is derived, but, like benzoilol, is formed in the 
process, by the reaction of principles not yet examined. 

It absorbs dry chlorine gas, and forms chlorinized sali- 
cylol, C 14 H 5 C10 4 ; bromine and iodine yield similar com- 
pounds. Salicylol is metameric with benzoic acid. 

By the action of ammonia upon an alcoholic solution of the 
oil, hydrosalimide is formed. Like hydrobenzamide, it is 
derived from three equivalents of the oil and two of ammonia, 
by the abstraction of 6HO. Its formula is C 42 H, 8 N 2 6 ; it 
crystallizes in brilliant yellow prisms, and is decomposed by 
both acids and alkalies, with the regeneration of the oil and 
ammonia. 

760. Salicylic Acid, C u H 6 6 . — This is formed from the 
oil by the union of two equivalents of oxygen : when sali- 
cylol is heated with hydrate of potash, the salicylate is 
formed ; this is decomposed by hydrochloric acid, which pre- 
cipitates the salicylic acid. It is white, crystallizable, volatile, 
and sparingly soluble in water, resembling benzoic acid. It 
is monobasic, and forms a large class of salts, which are of 
but little importance. 

761. When a mixture of salicylic acid, sulphuric acid, and 
wood-spirit are distilled, the salicylic methylic ether is 
obtained. It contains the elements of one equivalent of the 
acid and one of the spirit, minus two of water, and by the 
action of alkalies is decomposed into a salicylate and wood- 



392 ORGANIC CHEMISTRY. 

spirit. This ether is remarkable as constituting the oil of 
wmtergreen, Gaultheria procumbens : it is obtained in 
large quantities by distilling the plant with water. When 
placed in a close vessel of strong ammonia it slowly dis- 
solves, and the liquid by evaporation yields wood-spirit, and 
finally crystals of salicylamide, which is an amide of 
salicylic acid, and contains the elements of salicylate of 
ammonia minus two of water. Like the other amides, it is 
readily decomposed by acids and alkalies, by the action of 
which it combines with the elements of water, and regene- 
rates the original compounds. The mode of its formation 
will be readily understood by referring to what has been said 
of the relations between the ethers and amides, (705.) The 
alcohol minus two equivalents of hydrogen, may be viewed 
as substituted for two of oxygen in the acid : the ammonia 
gives up two elements of hydrogen, regenerating the alcohol, 
and the residue takes the place occupied by the residue of 
the alcohol, producing an amide in place of the ether. The 
ethers of almost all acids yield amides in this way, by the 
action of ammonia. 

762. By the action of strong nitric acid upon salicylic 
acid, nitrosalicylic acid is formed, by a reaction similar to 
that yielding the nitrobenzoic acid, (755.) It forms white 
crystals, very sparingly soluble in water. When fuming 
nitric acid is gradually added to the oil of wintergreen, the 
nitrosalicylic ether of wood-spirit is obtained ; it forms 
delicate yellow crystals, which are soluble in alcohol. 

763. When salicylic acid is rapidly distilled, it is decom- 
posed into carbonic acid and phenol, C^HgOa.C^HeOe = 
2C0 2 + C 12 H 6 2 . Phenol is found in the oil distilled from 
coal-tar, and according to Wohler constitutes the essential oil 
of Castor eum, a secretion of the beaver. It forms colorless 
crystals, which are liquefied by the least trace of moisture, 
and is generally obtained as an oily fluid, of a burning taste, 
and pungent, disagreeable odor, resembling that of wood- 
smoke. With the alkalies it forms crystalline compounds, 
and has hence been considered an acid, and described by the 
name of carbolic acid. By the action of chlorine gas, five 
new products are obtained, in which one, two, three, four, or 
five equivalents of hydrogen are replaced by chlorine : these, 
like the original compound, act as acids. By the action of 
nitric acid, phenol yields a compound in which two equiv- 
alents of nitrous acid are united, as in binitrobenzene, (757.) 



OIL OF CINNAMON. 393 

The final product of the action of nitric acid, is a substance 
in which the substitution of the hydrogen is complete, C 12 H 6 
2 + 3NH0 6 =C 12 3(NH0 4 )0 2 + 6HO. The whole of the hy- 
drogen combines with the oxygen of the acid, and is replaced 
by the residue of the latter. This substance, which may 
be designated as tri-nitrophenol, has been described by 
different chemists as nitrophenisic, carbazotic, nitropicric, 
and picric acids. It is the final product of the action of 
nitric acid upon a great variety of organic substances ; an 
easy method of obtaining it is by boiling salicylic acid, or 
oil of wintergreen, with strong nitric acid, till all action has 
ceased, and the red vapors of nitric acid no longer appear. 
The excess of carbon in the salicylic acid is expelled in the 
form of carbonic acid. Nitrophenisic acid forms yellowish 
white crystalline scales, which are slightly soluble in water ; 
the solution has a yellow color, and an intensely bitter 
taste.* 

Its salts have a yellow color, and explode violently when 
heated. The acid is monobasic, and if we represent the acid 
by C 12 H 3 N 3 14 , its potash salt will be C 12 H 2 KN 3 I4 ; this is a 
yellow crystalline powder, very sparingly soluble in water. 
Although this substance and the other derivatives of phenol 
yield salts with bases, they appear incapable of forming 
ethers or amides, and perhaps ought not to be considered as 
acids. 

OIL OF CINNAMON, C 18 H 8 2 . 

764. Cinnamol. — This fragrant oil is obtained by distilling 
the bark of cinnamon with water. It is a heavy fluid, 
soluble in water, and possesses in a high degree the taste and 
odor of cinnamon. When exposed to the air, it absorbs two 
equivalents of oxygen, and is converted into cinnamic acid, 
C 18 H 8 4 . Cinnamate of potash is formed with the evolution 
of hydrogen, when cinnamol is heated with hydrate of pot- 
ash. This acid is associated with the benzoic in the balsam 
of Tolu, and resembles it in its properties. When heated 
with nitric acid it is decomposed, and yields benzoic acid and 
benzoilol. 

* Whence the name picric, from the Greek piJcros, bitter. 



394? ORGANIC CHEMISTRY. 

SUGAR, STARCH, AND ALLIED SUBSTANCES. 

765. Under this head is included a class of substances of 
vegetable origin, which agree in containing carbon with oxy- 
gen and hydrogen in the propertions which form water. 
When soluble, they are insipid or have a sweet taste, and are 
generally nutritious. They are not volatile, and are readily . 
decomposed by heat or other agents. 

766. Sugars. — These bodies are soluble in water, have a 
sweet taste, and by the process of fermentation yield alcohol 
and carbonic acid. 

Cane Sugar, C^HnOn. — This occurs in the juices of 
many plants, as the sugar-cane, maple, beet-root, and Indian 
corn. It is obtained by evaporating the juice to a syrup, 
when the sugar crystallizes in grains of a brownish color. 
It is obtained pure and white by redissolving it, and fil- 
tering the solution through animal charcoal, (337.) By 
the slow evaporation of a concentrated solution, it is obtained 
in fine transparent crystals, which are derived from an oblique 
rhombic prism ; in this state it constitutes rock-candy. It 
fuses at 356°, and forms on cooling a vitreous mass, well 
known as barley sugar; this gradually becomes opaque, 
and changes into a mass of small crystals of ordinary sugar. 
Sugar is soluble in about one-third its weight of water, form- 
ing a thick syrup. It is insoluble in pure alcohol. 

767. Grape Sugar; Glucose, C,2Hi 2 12 + 2Aq. — This 
sugar is found in the grape and many other fruits, and in 
honey. It is formed when cane sugar or starch is boiled with 
dilute sulphuric acid, and is a product in many other trans- 
formations. The urine in the disease called diabetes melli- 
tus contains a large quantity of grape sugar, which is formed 
from the starch and similar substances taken as food. 

Grape sugar is generally obtained as a white granular 
mass, which requires one and a half parts of cold water to 
dissolve it ; it is less sweet to the taste than cane sugar, and 
about two and a half times as much are required to give an 
equal sweetness to the same volume of water. When heated 
to 212°, the two equivalents of water are expelled. With 
sulphuric acid, grape sugar forms a coupled acid, the sul- 
phosaccharic. If a solution of grape sugar is mixed with a 
solution of potash, and then with a little sulphate of copper, 
the liquid becomes dark, and soon deposits suboxyd of copper 
in the form of a red powder. Cane sugar yields no precipi- 



SUGAR, STARCH, AND ALLIED SUBSTANCES. 395 

tate until the solution is boiled. This test enable us to detect 
the 10 ^ do part of grape sugar in a liquid. 

768. Sugar of Milk; Lactine, Ci 2 H, O 10 + 2Aq. — This 
is found only in the whey of milk, and is obtained by evapo- 
rating it, and purifying the product by crystallization. 
Lactine forms semi-transparent prisms, soluble in six parts 
of cold water, and two and a half of boiling water ; it is 
much less sweet than cane or grape sugar. By a heat of 
212° its water is expelled ; by boiling with dilute sulphuric 
acid, it combines with the elements of two equivalents of 
water, and is converted into grape sugar. 

769. Mannite, C 6 H 7 6 . — This substance is not a proper 
sugar, and is not susceptible of fermentation. It exists in the 
juice of celery and many sea-weeds ; and constitutes the 
principal part of the manna of the shops, which is the concre- 
ted juice of a species of ash. When this is dissolved in 
hot alcohol, the mannite is deposited by cooling. It forms 
delicate silky crystals, which are slightly sweet and very 
soluble in water. 

Products of the decomposition of the Sugars. 

770. The vinous fermentation. — When the juice of grapes 
or other fruits containing sugar is exposed to the air, a pecu- 
liar decomposition ensues, in which the sugar is resolved into 
carbonic acid gas and alcohol. A solution of pure sugar is 
not changed by exposure to the air ; but if there is added to 
it a little yeast, or the juice of any fruit in the state of fer- 
mentation, decomposition takes place, and carbonic acid and 
alcohol are formed. Many substances besides yeast will 
effect this change, as blood, albumen, or flour paste in a state 
of decomposition. It appears that the influence of a ferment 
depends on the condition rather than the kind of matter. 
Any nitrogenized substance capable of undergoing putrefac- 
tion produces the same effect, and we are to attribute this 
change, in the juice of fruits, to a small portion of albumi- 
nous matter present. The mode in which these substances 
act is not understood, but it is supposed that when in a state 
of decomposition, they are able to induce a similar state in 
other substances with which they are in contact ; the equili- 
brium of the atoms in the compound is thus disturbed, and 
the elements arrange themselves in new forms. 

771. The conversion of grape sugar into alcohol and car- 
bonic acid is very simple ; one equivalent of dry grape sugar, 



396 ORGANIC CHEMISTRY. 

C^H^Otf, contains the elements of two equivalents of alcohol 
and four of carbonic acid gas : 

2 equivalents of alcohol, 2 X (C 4 H 6 2 ) = CgH^ 

4 " " carbonic acid gas, 4 X COa = C4 0$ 



I " " grape sugar, = C12H12O12 

Grape sugar is the only kind which is capable of this fer- 
mentation; and although the others readily yield alcohol 
and carbonic acid, it is found that the first effect of the fer- 
ment is to transform them into grape sugar by the assimila- 
tion of the elements of water. 

Many juices of fruits readily become sour by exposure to 
the air, especially if the quantity of sugar which they con- 
tain, and consequently the portion of alcohol that can be 
formed, is small. But in these cases, the formation of the 
acid, which is the acetic, is probably preceded by that of 
alcohol. 

772. When sugar is mixed with caseine (cheese curd) and 
exposed to a temperature of from 95° to 104°, a peculiar fer- 
mentation takes place, which produces a slimy substance that 
renders the liquid viscid. The other products are mannite 
and lactic acid, CgHgOe. The gummy matter is identical in 
composition with sugar. 

Similar products are obtained when the juices of beets and 
carrots ferment at a high temperature. This has been termed 
the viscous fermentation. When caseine or any other animal 
matter in an advanced state of decomposition is employed, it 
induces the alcoholic fermentation ; but at an earlier stage of 
the decay the action is different, giving rise to lactic acid and 
mannite. 

When milk is exposed to a temperature from 95° to 104°, 
it undergoes the vinous fermentation, and forms alcohol. It 
is well known that some nations prepare an intoxicating 
liquor by the fermentation of milk. In this process, a small 
quantity of acid is first formed, which converts the lactine 
into grape sugar. The elevated temperature promotes the 
decomposition of the caseine present, and thus enables it to 
produce this fermentation. Milk at ordinary temperatures 
becomes directly acid, without the previous formation of 
alcohol, and its sugar is then transformed into lactic acid. 

773. Lactic Acid, C 6 H 6 6 . — This acid may be obtained 
/ram sour milk, but is more easily prepared by the fermenta 
(ion of sugar with caseine. Fourteen parts of cane sugar 



SUGAR, STARCH, AND ALLIED SUBSTANCES. 397 

are dissolved in sixty of water ; to the solution is then added 
four parts of the curd from milk, and five parts of chalk to 
neutralize the acid which is formed. This mixture is kept 
at a temperature of 77° to 86° F. for two or three weeks, or 
until it becomes a crystalline paste of lactate of lime. This 
is pressed in a cloth, dissolved in hot water, and filtered; the 
solution is then concentrated by evaporation. On cooling, it 
deposits the salt in crystals, which may be purified by re- 
crystallization. This process yields about thirteen and a 
half parts of the crystallized lactate, and a small quantity 
of mannite. The reaction is very simple ; one equivalent 
of dry grape sugar, C 12 Hi 2 0, 2 , contains the elements of two 
equivalents of lactic acid, 2(0^06.) The mannite is the 
result of a secondary decomposition, and with certain pre- 
cautions, lactic acid is the only product. The carbonate of 
lime serves only to neutralize the acid formed. The lactate 
of lime may be decomposed by the careful addition of oxalic 
acid, which precipitates the lime, and the solution of lactic 
acid thus obtained, is concentrated by evaporation, and purified 
by solution in ether. It is a syrupy liquid, of specific gravity 
1-215, and is strongly acid to the taste. 

774. When lactic acid is heated to 482°, a white crystal- 
line substance sublimes which is called lactide ; it is* derived 
from the acid by the abstraction of the elements of two equi- 
valents of water, and has the formula C 6 H 4 4 . It is soluble 
in alcohol, but scarcely soluble in water ; by long continued 
boiling with it, however, it is converted into lactic acid. This 
acid is monobasic, and its salts are generally soluble and 
crystallizable. The lactate of lime (C 6 H 5 Ca0 6 ) crystallizes 
in fine prisms, with five equivalents of water. The lactate 
of zinc is obtained by decomposing a hot concentrated solu- 
tion of lactate of lime by chlorid of zinc; the salt crystallizes 
in cooling in beautiful colorless prisms. The lactate of iron 
(C 6 H 5 Fe0 6 ) is sparingly soluble in cold water, and may be 
prepared by a similar process ; it is employed in medicine. 

775. When the mixture of sugar, chalk, and curd is kept 
I* at a higher temperature, about 90°, a different action takes 

place; hydrogen gas is evolved, and butyrate of lime is 
formed. This product will be afterwards described. 

The action of chromic acid upon sugar yields formic acid, 
(740.) Dilute nitric acid forms, with cane and grape sugar, 
saccharic acid, C^H^Ou ; it is bibasic ; strong nitric acid 
converts them into oxalic acid. 
34 



398 ORGANIC CHEMISTRY. 

776. When sugar is- added to a concentrated solution of 
three times its weight of hydrate of potash and heated, the 
mixture becomes brown, and hydrogen gas is evolved. When 
the action ceases, and the mass is cooled, dissolved in water, 
and distilled with dilute sulphuric acid, it yields formic and 
acetic acids, with a new acid, the metacetonic, which is 
obtained as a volatile liquid, with a pungent acid odor. It is 
monobasic, and has the formula CeHgC^ : it is therefore a 
homologue of formic and acetic acids. 

A mixture of sugar and quick lime when distilled affords 
acetone, and an oily liquid called metacetone : this is related 
to the metacetonic acid as acetone is to the acetic, and yields 
that acid when distilled with a mixture of bichromate of 
potash and sulphuric acid. Mannite, starch, and gum, afford 
the same results with hydrate of potash and lime. 

777. Gum, C 12 H 10 O 10 . — This substance is best known in 
gum arable ; the gum which exudes from the cherry and 
plum, the mucilage of flaxseed, and many other plants, are 
identical with it. Gum is soluble in water, and forms a 
viscid solution, from which alcohol precipitates it unchanged. 

When boiled with dilute sulphuric acid, it is converted 
into grape sugar. With nitric acid, gum and milk sugar 
yield the mucic acid, which distinguishes them from all 
the other bodies of this class. The mucic acid is a white 
crystalline powder, which is sparingly soluble in water ; it is 
Dibasic, and is represented by the formula C 12 H 10 O 16 . It is 
consequently metameric with the saccharic acid, although 
quite different in its properties. 

778. The Pectic Acid, which is extracted from many 
fruits, appears to be nothing but a modified form of gum, 
and yields grape sugar with dilute acids. It combines with 
lime and some other bases to form compounds, which have 
been described as pectates. Both gum and sugar have also 
the property of exchanging one or two equivalents of hy- 
drogen -for lead, barium, or calcium, to form similar com- 
binations. 

779. Starch, C 12 Hi O 10 . — This substance exists in a great 
variety of vegetables. It is found in all the cereal grains, 
in the roots and tubers of many plants, as the potato, and 
in the bark and pith of various trees. It is obtained by 
bruising wheat and washing it in cold water, which holds the 
starch in suspension, and deposits it on standing. Potatoes 
furnish a large portion of starch by a similar process. The 



SUGAR, STARCH, AND ALLIED SUBSTANCES. 



399 




substances known as arrow-root, sa- 
lep, sago, and tapioca, are varieties 
of starch, obtained from different 
plants, and sometimes altered by the 
heat employed in drying. 

When examined by the naked eye 
it is a white shining powder, but under 
the microscope is seen to consist of 
irregular grains, which have a rounded 
outline, and are composed of concentric 
layers, covered with an external mem- 
brane. The diameter of the grains of 
potato starch is about j^ of an inch. 

Starch is insoluble in cold water, but if the mixture is 
heated, the globules swell, burst their envelopes, and form a 
transparent jelly, which is characterized by producing a 
deep-blue color with a solution of iodine. 

When the solution of starch is mixed with a little acid or 
an infusion of malt, and gently heated, it becomes very fluid, 
and is changed into dextrine* This has the same com- 
position as starch, but is very soluble in cold water, and is 
not colored blue by iodine. If starch is heated to 300° or 
400°, it is rendered soluble in water, and possesses all the 
properties of dextrine. In this state it is used in the arts as 
a substitute for gum, under the names of British Gum and 
leiocome. When dextrine is boiled for some time with 
dilute sulphuric acid, it is converted into grape sugar. 
It has been mentioned that grape sugar is formed in this way 
from starch ; but its formation is always preceded by that 
of dextrine. One part of starch may be dissolved in four 
parts of water, with about one-twentieth of sulphuric acid, 
and the mixture boiled for thirty-six or forty hours. The 
liquid is then mixed with chalk to separate the acid, and by 
evaporation and cooling affords pure grape sugar. Oxalic 
acid may be substituted for the sulphuric, with the same 
result. Starch sugar is extensively manufactured in Europe, 
and is often used to adulterate cane sugar. In this process 
the starch combines with the elements of two equivalents of • 
water, C 12 H 10 O 10 + 2HO=C 12 Hi2O 12 ; the acid is obtained at 



* So named, because when a beam o/ polarized light is passed 
through the solution, it causes the plane of polarization to deviate 
to the right hand. 



4*00 ORGANIC CHEMISTRY. 

the end of the process quite unaltered, and one part of acid 
will saccharify one hundred of starch, by long continued 
boiling. Starch or dextrine unites with sulphuric acid to 
form a coupled acid ; and it is probable that this is first 
formed, and then destroyed by boiling : at the moment of 
decomposition, the liberated dextrine takes up the elements 
of water necessary for the formation of sugar. A small 
portion of the coupled acid is always found in the solution. 

780. The action of an infusion of malt upon sugar is 
peculiar ; this substance is prepared from barley, by 
moistening the grain with water, and exposing it to a gentle 
heat till germination takes place, when it is dried in an oven 
at such a temperature as to destroy its vitality. The grain 
now contains a portion of starch sugar, and a small portion 
of a substance called diastase,* to which its peculiar 
properties are due. It is precipitated by alcohol from a 
concentrated infusion of malt, as a white flaky substance, 
which contains nitrogen, and is very prone to decomposition. 
When a little diastase is added to a mixture of starch and 
water, at a temperature of from 130° to 140°, the starch is 
soon converted into dextrine, and in a few hours into grape 
sugar. The action of an infusion of malt is due solely to the 
presence of a minute portion of this substance, one part of 
which will convert two thousand parts of starch into sugar. 
This effect appears to be due to a peculiar state of the 
diastase, which is a portion of the azotized matter of the 
grain in a modified form, and is analogous to that of ferments, 
already alluded to. 

781. Woody Fibre; Cellulose, C 12 H 10 O 10 . — This sub- 
stance is the solid insoluble part of vegetables, and remains 
when water, alcohol, ether, dilute acids and alkalies, have 
extracted from wood all its soluble portions. It is nearly 
pure in paper or old linen. Cellulose is identical in com- 
position with starch and dextrine, and by the action of strong 
sulphuric acid is dissolved and converted into that substance. 
This experiment is easily made with unsized paper or cotton ; 
to two parts of this, one part of the acid is very slowly added, 
taking care to prevent an elevation of temperature, which 
would char the mixture. In a few hours the whole is 
converted into a soft mass, which is soluble in water, and is 

* From the Greek diistemi, to separate, because it separates the 
insoluble envelopes of the starch globules. 



SUGAR, STARCH, AND ALLIED SUBSTANCES. 401 

principally dextrine. If the mixture is now diluted with 
water and boiled for three or four hours, the dextrine is com- 
pletely converted into grape sugar, which is obtained by 
neutralizing the acid with chalk, and evaporation. By this 
process paper or rags will yield more than their weight of 
crystallizable sugar. 

782. The mutual convertibility of these different sub- 
stances is interesting in relation to many of the phenomena 
of vegetable life. The starch in the germinating seed is 
changed by the action of diastase into sugar, in which 
soluble form it seems better fitted for the nourishment of the 
embryo plant. In the growth of this, we have an example 
of the formation of cellulose from sugar, in which this 
substance assumes a structural form under the action of the 
vital force. This is a transformation from the unorganized 
to the organized, which mere chemical affinity can never 
effect. 

783. Many unripe fruits, as the apple, contain a large 
quantity of starch, but no sugar. After the fruit is fully 
grown, the starch gradually disappears, and in its place we 
find grape sugar. This change constitutes the ripening of 
fruits, and as it is well known, will take place after they are 
gathered. In this process we have clearly a conversion of 
the starch into sugar, by the agency of the vegetable acids 
present in the fruit, a change which is the reverse of the 
previous one, and is probably independent of life. 

784. Xyloidine ; Gun Cotton. — When starch is rubbed 
in a mortar with nitric acid of specific gravity 1*5, it forms 
a gelatinous mass from which water precipitates xyloidine. 
When dry, it is a white powder, which takes fire at a low 
temperature and burns with great vivacity. Its composition 
is C^HgNO^, and it is derived from starch, by the addition 
of one equivalent of nitric acid and the abstraction of the 
elements of two of water, Ci 2 H 10 O 10 + NH0 6 = Ci 2 H 9 N0 14 
+ 2HO. The nitric acid less 2 may be viewed as repre- 
senting H 2 in the starch, and we may write the formula 
C 12 H s (NHO 4 )O 10 , (675.) 

The action of strong nitric acid upon woody fibre gives 
origin to another substance, which has lately attracted great 
attention as a substitute for gunpowder, under the name of 
gun cotton, and which Mr. Pelouze has called pyroxyline. 
Paper, saw-dust, or any other form of cellulose, by digestion 
iu strong nitric acid, acquires a considerable increase of 
34* 



402 ORGANIC CHEMISTRY. 

weight, and is converted into this new substance ; but it is 
best obtained from cotton. The following is an outline of 
the process : one hundred grains of clean cotton are im- 
mersed for five minutes in a mixture of an ounce and a half 
of nitric acid of specific gravity 1*45 to 1*5, with the same 
measure of strong sulphuric acid ; it is then removed, care- 
fully washed in cold water from every trace of acid, and 
dried at a temperature which should not exceed 120°. As 
thus prepared it preserves the form of the cotton unaltered, 
but has less strength than the original fibre. It inflames by 
a very gentle heat; sometimes under circumstances not 
well understood, it has been observed to take fire at 212° F. 
Its combustion is instantaneous, accompanied by an immense 
volume of flame, and it leaves not the slightest residue. 
When ignited in a confined space, it explodes with great 
violence: one-tenth of a grain is sufficient to shatter the 
strongest glass tube. Its power in propelling balls is about 
eight times greater than that of gunpowder. Its tremendous 
energy depends upon the fact that it is completely resolved, 
by its combustion, into aqueous vapor and permanent gases, 
which are carbonic oxyd, carbonic acid, and nitrogen. As 
these are much less noxious than the gases resulting from 
the combustion of gunpowder, the gun cotton will be found 
of great use in mining. Its analysis is very difficult, on 
account of its explosiveness ; but from the results of Pelouze 
and others, it appears to be derived from two equivalents of 
cellulose and five of nitric acid, with the abstraction of ten 
of water : 2C 12 H 10 O 10 = C^H*0„+5NH0 6 = C 24 H 15 N 5 O 40 -f 
10HO. There are reasons for supposing that the equivalent 
of cellulose and all the allied substances should be doubled, 
and this substance will then be cellulose, C^H^C^o, in which 
the residue of five equivalents of nitric acid replaces ten of 
hydrogen, which have formed water with the oxygen of the 
acid. Its formula may then be written C^H^NHO^Oa©. 
This formula requires that 100 parts of cellulose should 
yield 169*1 of pyroxyline, and experiment gives 170 to 172 
parts. It is very difficult to dry it perfectly, for it is gradually 
decomposed at 212°, and often explodes at that temperature : 
hence the analyses have invariably given a little more 
oxygen and hydrogen than the formula requires. Pyroxy- 
line, when pure, is soluble in the acetic ethers of alcohol and 
wood-spirit. 



SUGAR, STARCH, AND ALLIED SUBSTANCES. 403 

Transformation of Woody Fibre. 

785. By the action of atmospheric air and moisture, wood 
undergoes a slow decay, dependent on the absorption of oxy- 
gen, to which Liebig has applied the term eremacausis* 
The carbon is converted into carbonic acid, while the oxygen 
and hydrogen of the lignine unite to form water. The resi- 
due is still found to contain oxygen and hydrogen in the 
original proportions, but the relative amount of carbon is 
continually increasing. For each equivalent of carbonic 
acid two of water are evolved. The final result of this pro- 
cess is a brown or black residue, which constitutes vegetable 
mould. Different products of this decomposition have been 
described under the names of humus, geine, ulmine, humic 
and ulmic acids. 

Nearly all of these bodies contain ammonia, for which 
they have a strong affinity ; this is in part absorbed from the 
air, but the late experiments of Mulder have shown that they 
have the power of forming ammonia from the nitrogen of 
the atmosphere. Pure humic acid moistened and placed in a 
close vessel filled with air, is found after some months to 
contain a considerable quantity of ammonia. The hydrogen 
evolved by a slow decomposition of the water, is brought into 
contact with nitrogen under such conditions, that they com- 
bine and produce the alkali. 

786. The decomposition of wood, when buried in the 
ground and excluded from the action of the air, is very dif- 
ferent. The oxygen which it contains, gradually combines 
with the carbon to form carbonic acid, and substances are 
obtained, in which the proportion of carbon and hydrogen is 
greater than in the original fibre. Peat, lignite, and bitu- 
minous coal, are products of this decomposition. The car- 
bon and hydrogen in coal combine in various ways, and often 
generate vast quantities of gaseous carburets of hydrogen, 
(450.) Anthracite has resulted from the action of heat on 
bituminous coal, which has expelled all the volatile ingre- 
dients, and left a residue of nearly pure carbon. 

Destructive Distillation of Wood. 

The principal products of the decomposition of wood by 

* From crema, slow, and kausis, combustion, a term by which 
that chemist denotes those changes which take place in organic 
bodies from the gradual action of oxygen. 



404 ORGANIC CHEMISTRY. 

heat, are acetic acid and pyroxylic spirits, and have been 
already described, (720, 734). Beside these a quantity of 
viscid tarry matter is obtained, which contains many very 
interesting compounds. 

787. Kreasote. — This substance occurs dissolved in the 
crude acetic acid from wood, and is separated and purified 
by a complicated process. It is a colorless oily fluid, which 
boils at 397°, and has a specific gravity of 1-037; it has a 
peculiar and very persistent odor resembling that of smoke, 
and a powerful burning taste. It is soluble in about 100 parts 
of water, and the solution possesses powerful antiseptic 
qualities. Meat which has been soaked in it, is incapable of 
putrefaction,* and acquires a delicate flavor of smoke. 
The power of wood smoke to preserve flesh, is due to the 
presence of kreasote. It is a corrosive poison when taken in 
any quantity, but a very dilute solution is used medicinally, 
both internally and externally, as a styptic and antiseptic. It 
is often applied to the nerve of a decayed tooth, and in this 
may relieve the pain of tooth-ache, but its use requires care, 
for if brought in contact with the lining membrane of the 
mouth, it instantly destroys its vitality. 

788. The composition of kreasote is C 14 H 8 2 ; by the 
action of nitric, it yields nitrophenisic acid, (763). It com- 
bines with the alkalies to form crystalline compounds. 

Wood-tar contains several carburets of hydrogen, one of 
which, called eupione, is an oily, fragrant liquid, of the 
specific gravity -655, being the lightest liquid known. Its 
formula is, probably, C 6 H 6 . 

Para fine. — This is a white crystalline substance, ob- 
tained from the less volatile portions of wood-tar. It crys- 
tallizes in delicate needles, which fuse at 110° ; it is soluble 
in alcohol and ether. Its formula is C 48 H 50 . Paraffine is 
obtained in large quantities by the dry distillation of bees- 
wax. 

789. Coal Tar consists principally of a mixture of 
various hydrocarbons ; some of these are liquids and quite 
volatile, constituting what is called gas naphtha. Among the 
less volatile products, are two solid carburets of hydrogen, 
naphthalene, and paranaphthalene, or anthracene. The first 
of these is formed by the decomposition of many organic 
matters by heat. Its formula is C^Hg ; it is volatile, and 

* Hence the name, from the Greek Areas, flesh, and soto, I preserve. 



FATS AND THE SUBSTANCES DERIVED THEREFROM. 405 

forms beautiful pearly crystals of a fragrant odor. The 
action of chlorine, bromine, and nitric acid on naphthaline, 
gives rise to a great number of compounds, which have lately 
been studied by Laurent. They are formed by successive 
substitutions of the hydrogen by one or more of these sub- 
stances, and many metameric modifications of these bodies 
exist. Thus, the bichlorinized naphthaline, C 20 H 6 C1 2 , occurs 
in seven modifications, which are perfectly distinct in their 
characters. We are forced to suppose that these compounds 
owe their different properties to a different arrangement of 
their constituent atoms, and it is easy to see that, in this 
way, the number of possible combinations will be immense. 
More than twenty substances have been described, in which 
chlorine is in part substituted for the hydrogen of the naph- 
thaline. The final product of the action of chlorine is 
C 20 C1 8 , being a chlorid of carbon, which preserves the type 
of naphthaline. In addition to these, coal-tar contains a con- 
siderable proportion of phenol or carbolic acid, (763) and 
two organic alkaloids, named hyanol and leukol. The 
watery products of the distillation of coal hold a large 
quantity of ammonia in solution, often combined with hydro- 
sulphuric and hydrocyanic acids. 

790. Petroleum. — Tn many parts of the world, an oily 
matter exudes from the rocks, or floats on the surface of 
springs. The principal sources of this substance are Amiano 
in Italy, Ava, and Persia, but it is found in many places in 
our own country. The well known Seneca Oil is an in- 
stance of this kind. Petroleum is a variable mixture of 
several bodies. By distillation, it yields a colorless liquid 
called naphtha, which is very light, volatile, and combustible. 
Its formula is C 6 H 3 . Naphtha occurs nearly pure in Italy and 
Persia, and is used for illumination. 

Petroleum contains a variety of other bodies, among which 
are parajjine, arid several resinous matters, formed perhaps 
by the oxydation of naphtha. These substances are probably 
derived from coal or other matters of vegetable origin. 

FATS AND THE SUBSTANCES DERIVED FROM THEM. 

Glycerides. 

791. Under the general name of fats is included a large 
class of bodies of animal and vegetable origin, which are 
characterized by being insoluble in water, combustible, and 



406 



ORGANIC CHEMISTRY. 



volatile only at high temperatures with decomposition. Some 
of them, as the oils, are liquid at common temperatures, 
while others, as mutton tallow, require a heat of 120° for 
their fusion. When digested with water and an alkali, or a 
basic metallic oxyd, they take up the elements of water, and 
are resolved into acids, which unite with the base, forming 
the compounds called soaps, and a peculiar sweet substance 
to which the name of glycerine* is given. 

Glycerine is most easily prepared by heating a mixture of 
olive oil, oxyd of lead, and water. The oil is decomposed, 
and the acids form insoluble salts with the lead, while the 
glycerine is dissolved in the water ; the solution is treated 
with sulphureted hydrogen to precipitate a little dissolved 
oxyd of lead, and evaporated in a water-bath. The formula 
of glycerine is C 6 H 8 6 . It is a colorless, syrupy liquid, of a 
very sweet taste, and is readily soluble in water and alcohol , 
it is not volatile, but when strongly heated is decomposed, 
evolving acetic acid, and other products, the most important 
of which is acroleine. This is obtained pure by distilling 
glycerine with anhydrous phosphoric acid; it is formed from 
it by the abstraction of the elements of four equivalents of 
water, C 6 H 8 6 — 4HO==C 6 H 4 2 , the formula for acroleine. 
It is a colorless liquid, having a powerful pungent odor, 
which irritates the eyes and nose exceedingly, and is the 
same smell that is evolved when fats are strongly heated. 
With sulphuric acid glycerine yields a coupled acid. 

792. All of the fats contain the elements of one equivalent 
of glycerine, and two of an acid minus six equivalents of 
water. For example : palmitine yields, by the action of 
alkalies, ethalic acid and glycerine, and its composition may 
be expressed by (C 6 H 8 6 + 2C 32 H 32 4 )— 6HO=C 70 H 66 O 8 . In 
its decomposition it takes up the elements of six equivalents of 
water, and regenerates glycerine and the acids. These sub- 
stances present some analogy to the ethers, (702,) and amides, 
(697,) in their mode of decomposition ; they are distinguished 
by the general name of glycerides. None of these are volatile 
without decomposition ; when distilled they yield some com- 
pound of carbon and hydrogen, a fatty acid, and acroleine ; 
the peculiar pungent odor of this last is characteristic of the 
glycerides. 

793. The ethalic acid, which results from the decomposi- 
tion of palmitine, has been already noticed as a derivative of 

* From the Greek glukus, sweet. 



FATS AND THE SUBSTANCES DERIVED THEREFROM. 407 

one of the alcohols, and phocenine, another gl yceride, yields, 
by its saponification, valerianic acid, which is a product of 
the oxydation of amylic alcohol. There are in addition to 
these a large number of fatty acids derived from the saponi- 
fication of glycerides, which are homologues of valerianic 
and ethalic acids, and these being the most important, will be 
first described. 

794. Butyric Acid, C 8 H 8 4 . — Butter is a mixture of 
several glycerides : the one to which it owes its agreeable 
flavor is called butyrine, and when saponified by an alkali 
yields butyric acid. It has been recently discovered that the 
fermentation of sugar under peculiar circumstances produces 
butyric acid, a fact referred to when describing sugar. A 
solution of sugar is mixed with a little curd of milk, and a 
sufficient quantity of chalk to saturate the acid which will 
afterwards be formed. The mixture is placed in a situation 
where the temperature is from 77° to 86° F. : the fermenta- 
tion is at first viscous, then lactic, and finally butyric : much 
hydrogen and carbonic acid gases are evolved, and the mix- 
ture emits a very unpleasant odor. After several weeks the 
evolution of gas ceases, and the liquid contains nothing but 
butyrate of lime. The operation succeeds best when con- 
siderable quantities are employed. The reaction is very 
simple. The sugar is probably first converted into grape sugar, 
one equivalent of which, C 12 H 1 20 1 2=C8H 8 4 + 4C0 2 -f H 4 . 

This acid is easily procured by distilling the butyrate of 
lime with hydrochloric acid ; it must be digested with chlorid 
of calcium, and redistilled to obtain it free from water. Pure 
butyric acid is a limpid colorless liquid, which is dissolved in 
all proportions by water and alcohol, boils at 327°, and has 
a specific gravity of -963. It has an odor resembling that 
of vinegar and strong butter, and an acid pungent taste. It 
is monobasic, and its salts are all soluble in water. The 
butyrate of lime (C 8 H 7 Ca0 4 ) dissolves readily in cold water, 
but its solubility diminishes as its temperature is elevated : at 
the boiling-point almost the whole of the salt separates in 
transparent prisms, which redissolve on cooling. 

Butyric Ether, C 12 H 12 4 . — This is formed with great 
facility by distilling a mixture of butyric acid and alcohol 
with sulphuric acid. It is a colorless liquid, slightly soluble 
in alcohol, and has an agreeable odor like pineapples. It is 
employed by distillers to flavor spirits. When a mixture of 
butyric acid and glycerine is heated with sulphuric acid, an 



408 ORGANIC CHEMISTRY. 

oily liquid separates which appears to be butyrine, and yields 
butyric acid and glycerine by action of alkalies. It is the 
only glyceride that has been formed artificially. 

When butyrate of lime is distilled it affords butyrone, cor- 
responding to acetone (733), and a light colorless fluid called 
butyral. This has the formula C 8 H 8 2 , and sustains the 
same relation to butyric acid that aldehyde does to the acetic ; 
when exposed to the air it absorbs two equivalents of oxygen, 
and forms butyric acid. 

795. The oil of the porpoise contains a peculiar glyceride 
called phocenine ; by the action of alkalies it affords gly- 
cerine and valerianic acid (745), which has been described 
under the name of phocenic acid. 

The saponification of butter affords, in addition to the 
butyric, the volatile acids called caproic, caprylic, and capric. 
They are separated from each other and from butyric acid 
by the different solubility of their barytic salts. The caproic 
acid is Ci 2 H 12 4 . It is an oily liquid, slightly soluble in water, 
and has an odor which resembles at the same time that of 
vinegar and of sweat. The caprylic (Ci 6 H 16 4 ) and the 
capric (C 20 H 20 O 4 ) are volatile odorous acids closely resembling 
the caproic. 

The action of nitric acid upon castor oil and some other 
fats, yields a volatile oily acid of a fragrant odor called the 
enanthylic : it is C ]4 H 14 4 . The distilled water of the rose 
geranium [Pelargonium roseum) contains another oily acid 
allied to the last ; it is called pelargonic acid, and is C 18 H 18 4 . 

796. The preceding acids are all volatile, odorous, more 
or less soluble in water, and although their boiling-points are 
often elevated, may be distilled over with its vapor. Their 
baryta and lime, salts are soluble in water. The remaining 
acids in the series are solid, crystalline, inodorous, and in- 
soluble in water ; their salts with a base of barium or calcium 
are insoluble, while the potash and soda salts are very soluble 
in water, .-and are proper soaps. 

797. The berries of the laurel, called Lavrus nobilis, con- 
tain a white crystalline glyceride called laurine, which, when 
saponified, affords the lauric acid, C^EL^C^. It is white and 
crystalline, and fuses at 88° : alcohol dissolves it readily, and 
the solution has a strongly acid reaction. 

The oil of the cocoanut yields, by saponification, cocinic 
acid, C 26 H 26 4 : it is very fusible and resembles the last. 
The nutmeg contains a peculiar fat or glyceride called my- 



FATS AND THE SUBSTANCES DERIVED THEREFROM. 409 

ristine, which yields, by the usual process, myristic acid, 
C^H^O^ Tt resembles the preceding, and fuses at 120°. 

The palm oil, which is the product of the nuts of the 
Elais guinensis, is a mixture of a fluid fat, oleine, with 
a solid crystalline substance called palmitine. This is the 
glyceride of ethalic acid, which has been described under the 
name of palmitic acid. 

798. The solid fat of animals is composed of two solid 
glycerides, margarine and stearine, with a liquid called 
oleine.* The oil of olives and butter contains a portion of 
margarine. It is best obtained from animal tallow by dis- 
solving it in several times its volume of hot ether. The stea- 
rine crystallizes out on cooling, arM after expelling the ether 
by evaporation, the margarine is obtained mixed with oleine, 
which may be removed by pressure between folds of blotting- 
paper. Pure margarine fuses at 116°, and is very soluble in 
ether ; by the action of alkalies it yields glycerine and mar- 
garic acid. This acid is white, and crystallizes in pearly 
plates; it fuses at 140°. Its composition is 034113404. 

799. Stearine is obtained as a white crystalline mass, 
fusing at 130°. It is almost insoluble in alcohol and cold 
ether. By saponification it yields the stearic acid ; this is 
very soluble in ether and alcohol, and melts at 167°. Its 
formula is CagELjgCV The stearic ether is obtained by pass- 
ing hydrochloric acid gas through a hot solution of stearic 
acid in alcohol ; it is a white crystalline substance, soluble 
in alcohol, but insoluble in water ; it fuses at 88°, and by a 
higher heat, is completely decomposed. It is the homologue 
of acetic and butyric ethers, and like them is decomposed by 
an alcoholic solution of potash, taking up the elements of two 
equivalents of water, and regenerating alcohol and stearic 
acid. The ethers of the other fatty acids may be formed by 
a process similar to that just described, and are much more 
fusible than the acids themselves. 

800. Bees-wax may be regarded as the aldehyde of stearic 
acid ; its formula is CasH^C^, and it is consequently the 
homologue of spermaceti and butyral. When heated with 
hydrate of potash, hydrogen gas is evolved, and stearic acid 
formed. It is soluble in a solution of potash, and forms a 



* Stearine, from the Greek stear, tallow, and oleine, from elaion, 
oil. Margarine is named from margarites, a pearl, in allusion to 
the pearly lustre of its acid. 
35 



410 



ORGANIC CHEMISTRY. 



kind of soap ; when boiled with a very concentrated potash 
ley, it yields stearic acid and a volatile crystalline substance, 
which appears to correspond to the ethoi of spermaceti, and 
to be the alcohol of stearic acid. 

It has been regarded as a vegetable production, and col- 
lected by bees from plants ; but recent experiments have satis- 
factorily shown that bees produce wax when fed upon pure 
sugar or honey ; it must, therefore, be a secretion of the insect. 

The berries of the Anamirta coculus contain a peculiar 
glyceride, which by the action of alkalies yields the ana- 
mirtic acid. It closely resembles the preceding acids, and 
its composition is C X ]1 36 4 . 

801. The fatty acids aWeady described, are homologues 
of formic and acetic acid ; they are monobasic, contain four 
equivalents of oxygen, with carbon and hydrogen in equal 
equivalents. This will be seen by arranging them in suc- 
cession. 



1. 


Formic, 


C2 H2 O4 


11. 




C22H22O4 


2. 


Acetic, 


C4 H4 O4 


12. 


Laurie, 


C24H24O4 


3. 


Metacetonic, 


C6 H6 O4 


13. 


Cocinic, 


C26H26O4 


4. 


Butyric, 


Cg Hg O4 


14. 


Myristic, 


C23H28O4 


5. 


Valerianic, 


C10H10O4 


15. 




C30H30O4 


6. 


Caproic, 


C12H12O4 


16. 


Ethalic, 


C32H32O4 


7. 


Enanthylic, 


C14H14O4 


17. 


Margaric, 


C34H34O4 


8. 


Caprylic, 


C ]6 Hi 6 04 


18. 


Anamirtic, 


C36H36O4 


9. 


Pelargonic, 


Ci 8 H] 8 04 


19. 


Stearic, 


C38H38O4 


10. 


Capric, 


C20H20O4 









The first, second, fifth, and sixteenth of these acids are de 
rived from alcohols already known, and the bodies corres- 
ponding to aldehyde in the fourth and nineteenth, have also 
been discovered ; we may regard all of them as the acids of 
a series of alcohols as yet unknown. In this group we observe 
a regular transition from the acetic and formic acids, through 
the butyric, valerianic, and other oily sparingly soluble acids, 
to the completely insoluble ethalic and stearic. The eleventh 
and fifteenth of the series are as yet unknown, but it is 
highly probable that they may yet be discovered, as well as 
others higher in the series. Three or four of those in the list 
have been described within as many years. 

The first ten acids in the group which volatilizes without 
decomposition, exhibit a progressive increase of about 36° F. 
in their boiling-points; thus, the formic acid boils at 212°, 
the acetic at 212° + 36°= 248°, and the metacetonic, at 248° + 
36° =284°. 



FATS AND THE SUBSTANCES DERIVED THEREFROM. 411 

802. Oleic Acid. — The fluid portion of butter and animal 
fats consists principally of oleine ; and the vegetable and animal 
oils are composed of oleine and a little margarine, or other 
glycerides. It is obtained by exposing olive oil to cold, and 
separating the margarine which crystallizes out ; it is lighter 
than water, tasteless and inodorous. By the action of alkalies 
it yields glycerine and oleic acid. This resembles oleine 
itself, and has neither taste nor smell ; it rapidly absorbs 
oxygen from the air, and is altered. Its composition is 
C^H^C^, and it is monobasic, forming, like the other fatty 
acids, soluble salts with the alkalies. 

When nitrous acid vapor is passed through oleic acid, it 
almost immediately solidifies into a crystalline mass of 
elaidic acid, which is purified by crystallization from 
alcohol. It forms superb crystals of a brilliant whiteness, 
fusing at 112°. Its composition is precisely similar to oleic 
acid, of which it is a metameric modification. When oleic 
or elaidic acid is heated with hydrate of potash, hydrogen 
gas is evolved, and ethalate and acetate of potash are formed. 
If oleic acid is boiled for a few minutes with strong nitric 
acid, it is converted into margaric acid, which congeals on 
cooling : the reaction consists in the separation of two 
equivalents of carbon as carbonic acid gas. 

Stearic acid affords the margaric by a similar process. 
The prolonged action of nitric acid gives rise to the volatile 
acids of the preceding series. M. Redtenbacher has recently 
observed in the volatile products resulting from the action 
of nitric upon the oleic acid, all those from the acetic to 
the capric inclusive. The other fatty acids and wax yield 
the same products. 

803. The residue of this process contains four soluble, 
crystallizable, bibasic acids, the succinic, CgH^Og, adipic, 
C, 2 H 10 O 8 , pimelic, C 14 H 12 8 , and suberic, C 16 H 14 8 . The suc- 
cinic acid was originally obtained by distilling amber, a fossil 
resin, which occurs in recent geological formations. Succinic 
acid is soluble in water and alcohol ; when heated it fuses, and 
is decomposed into water and a neutral crystalline substance 
called succinide, C 8 H 4 6 , which when boiled with water is 
gradually reconverted into succinic acid. The other acids 
are of but little importance ; the suberic is a product of the 
action of nitric acid upon cork. When oleine or oleic acid 
is distilled, sebacic acid is obtained ; it is crystallizable, 
volatile, and soluble in water, and has the formula C^HigOg. 



412 ORGANIC CHEMISTRY. 

It is bibasic and homologous with the four preceding acids, 
in all of which the number of equivalents of hydrogen is less 
by two than the carbon, and the oxygen equal to eight 
equivalents. When these acids are fused with hydrate of 
potash, hydrogen gas is evolved, and salts of the volatile 
acids of the preceding groups are formed. The pimelic 
yields by this process valerianic acid ; carbonic acid is 
formed at the same time. 

804. Soaps. — The compounds of these acids are very 
important, and constitute the bodies generally known as 
soaps. These are mixtures of oleate, margarate, and 
stearate of potash or soda, being formed from the saponifi- 
cation of mixed fats by these alkalies. The soft soaps con- 
tain potash, and the hard ones soda. All these compounds 
are readily decomposed by acids, which combine with the 
alkali and liberate the fatty acid. When we mix a solution 
of soap with the soluble salt of any other base, we obtain a 
precipitate which is an insoluble combination of the fatty acid 
with the base. Hence the power of salts of lime or magnesia 
to render water hard. The compounds of these acids with 
the oxyd of lead, constitute the lead plaster, or diachylon, 
so much used in surgery. A mixture of stearic and mar- 
garic acids, obtained by saponifying animal fats with lime, 
and decomposing the insoluble soap by hydrochloric acid, 
has been employed in the manufacture of candles. When 
a solid fat, as lard, is kept for a long time melted, especially 
if a little spirit of wine is mixed with it, the solid portions 
separate, on cooling, in crystalline grains : by subjecting this 
mass to pressure, the fluid part is separated, and the mixture 
of margarine and stearine thus obtained is used for the manu- 
facture of candles, while the fluid oleine constitutes what is 
called lard oil. Both of these products are now extensively 
manufactured in this country. 

VEGETABLE ACIDS. 

805. Besides those vegetable acids already described, 
there are a number of others, most of which exist in saline 
combination in different plants. They are generally solid, 
crystallizable, soluble in water, and not volatile without 
decomposition. A few of the more important of them will be 
noticed. 

806. Oxalic Acid, C 4 H 2 8 . — The salts of this acid exist 



VEGETABLE ACIDS. 413 

in many vegetables : the agreeably sour taste of wood sorrel, 
Oxalis acetosella, and other plants of the same genus, is due 
to the acid oxalate of potash which they contain. Oxalic 
acid is a product of the action of nitric acid upon sugar, 
starch, lignine, and many other organic substances. To 
prepare it, one part of starch is heated with eight parts of 
nitric acid, specific gravity 1*25. A violent action ensues, 
and much nitrous acid is evolved ; when this ceases, the 
solution is concentrated by evaporation, and on cooling yields 
a large quantity of crystals of oxalic acid, which are purified 
by washing in water, and recrystallization. 

Oxalic acid is colorless, very soluble in water, has a 
powerfully acid taste, and is very poisonows. It crystallizes 
with four equivalents of water, in forms belonging to the 
monoclinite system : by a gentle heat the water is expelled, 
and the dry acid, C 4 H 2 8 , remains ; this, by a careful appli- 
cation of heat, may be in part sublimed unchanged, but at a 
high temperature it is decomposed into formic acid, water, 
and carbonic oxyd and carbonic acid gases. When oxalic 
acid or an oxalate is heated with strong sulphuric acid, it is 
decomposed, and a mixture of equal volumes of carbonic 
acid and carbonic oxyd gases is evolved, C 4 H 2 8 =2C0 2 -{- 
2CO + 2HO, (347.) 

807. Oxalic acid is bibasic, and forms neutral salts in 
which two equivalents of its hydrogen are replaced by a 
metal, and acid salts with but one equivalent of fixed base. 
The neutral oxalate of potash (C 4 K 2 8 ) is a very soluble 
salt. The acid oxalate, commonly called binoxalate (C 4 HK0 8 ) 
is less soluble, and has an agreeable acid taste. It exists, as 
before stated, in the juice of the Oxalis 'icetosella, and is 
hence often distinguished as salt of sorrel ; it is used to remove 
iron stains from linen, which it does by forming a soluble 
salt with the iron. When this oxalate is dissolved in hydro- 
chloric acid, a salt separates on cooling which is commonly 
called a quadr oxalate. Its composition is such that it may 
be regarded as a compound of equal equivalents of oxalic 
acid and the acid oxalate. The neutral oxalate of ammonia 
(C 4 H20 8 +2NH 3 ) crystallizes in fine prisms, and is much used 
in analytical chemistry. When exposed to heat, it is decom- 
posed, and yields, among other products, water and oxamide. 
This substance has been already described as the amide of 
oxalic acid, (698.) The acid oxalate yields in the same 
manner the acid amide, oxamic acid, which contains 
35* 




414 ORGANIC CHEMISTRY. 

C 4 H 2 8 >NH 3 -2HO=C 4 H 3 N0 6 . When a solution of oxamic 
acid is boiled, it reassumes the elements of water and forma 
acid oxalate of ammonia. 

808. The Oxalate of Lime (C 4 Ca0 8 -f4aq) is a very in- 
soluble salt, and occupies an important part in the vegetable 

economy, being secreted by a large number of 
plants, in the cells of which the microscope re- 
veals to us a great number of beautiful crystals 
of this substance; this appearance is repre- 
sented in the annexed figure of a vessel from 
the bark of Torreya taxifolia. In many of 
the lichens, the oxalate of lime appears to re- 
place the woody fibre, and to be somewhat 
allied in its functions to the carbonates and 

phosphates of lime in the animal kingdom. The oxalates of 

the metals are generally insoluble. 

809. Oxalic acid combines with two equivalents of the 
alcohols to form neutral ethers (703) ; they are obtained by 
distilling the alcohol and oxalic acid with a portion of sul- 
phuric acid. The oxalic methylic ether crystallizes finely ; 
those of spirit-of-wine and amylol are liquids. The oxalo- 
vinic is a coupled acid, which corresponds to the sulphovinic, 
(704.) When oxalic ether is mixed with excess of ammonia, 
alcohol separates, and oxamide is formed ; but if ammonia 
is cautiously added, only half of the alcohol is eliminated, and 
a beautiful crystalline compound called oxamethane is ob- 
tained ; it is an ether-amide, like sulphamethylane, (736.) 

810. Tartaric Acid, C 8 H 6 12 . — This acid exists in the 
juices of many fruits, particularly that of the grape, as an 
acid tartrate of potash. As this salt is almost insoluble in 
dilute alcohol, it is deposited, during the fermentation, in 
crystalline crusts known as crude tartar, or argol. It is 
decomposed by chalk to form a tartrate of lime ; this is 
mixed with an equivalent of sulphuric acid, which forms a 
sulphate, and liberates the tartaric acid. From a concentrated 
solution it crystallizes in fine rhombic prisms, very soluble in 
water and alcohol, and having a pleasant acid taste. Tartaric 
acid is bibasic, and often forms salts with two bases. 

811. The Acid Tartrate of Potash, C 8 H 5 K0 12 , is obtained 
by purifying the crude tartar of wine, and generally appears 
as a white crystalline powder, known as cream of tartar. 
It is very little soluble in cold water, and has a slightly acid 
taste ; it is extensively used in dyeing and in medicine. The 



VEGETABLE ACIDS. 415 

neutral tartrate, CgHJ^O^, is very soluble. The tartrate 
of potash and soda is obtained by neutralizing cream of 
tartar by carbonate of soda, and forms very large trans- 
parent prismatic crystals : it is commonly known by the 
name of Rochelle salt. When a mixture of water, cream 
of tartar, and oxyd of antimony is boiled together, solution 
takes place, and on cooling transparent crystals are deposited, 
which are employed in medicine under the name of tartar 
emetic. As oxyd of antimony is not a protoxyd, it obviously 
cannot replace the hydrogen equivalent for equivalent, but 
one equivalent of its oxygen combines with one of hydrogen 
from the acid, and the residues unite, C 8 H 3 KO ]2 — 0-f-Sb 2 3 
= C 8 (H 4 Sb 2 2 K)0 12 + HO. The salt contains, besides, ten 
equivalents of water of crystallization ; these are expelled by 
a gentle heat, but if the temperature is carried to 428° two 
more equivalents of water are given off, and a salt remains 
which is (^(HaSbaK^O^. Arsenious acid forms similar 
compounds. Tartaric acid dissolves peroxyd of iron, and 
forms a very soluble salt : in this as well as in the preceding 
compounds, the metal is so combined as not to be pre- 
cipitated by potash or ammonia. 

Tartaric acid yields with alcohol an ether and a coupled 
acid, the tartrovinic. When tartaric acid is heated it loses 
the elements of water, and forms several new acids which 
are of no particular interest. 

812. Racemic, or Parataric Acid, C 8 H 6 12 . — This acid 
is isomeric with the preceding, and is often associated with 
it in the juice of the grape. It is bibasic, and closely 
resembles the tartaric acid in its properties and the results of 
its decomposition by heat, but is distinguished from it by 
several characters ; it is less soluble, and crystallizes with 
one equivalent of water, while the crystallized tartaric acid 
is anhydrous ; the double racemate of potash and soda is 
very difficultly crystallizable, while the double tartrate crys- 
tallizes readily ; the racemic acid precipitates solutions of the 
salts of lime, which are not affected by the tartaric ; finally, 
the salts of the racemovinic acid are different from those of 
the tartrovinic. -* 

813. Malic Acid, CgHgOjQ. — This acid exists in the juices 
of most sour fruits, particularly in the apple.* The stems 
of the garden rhubarb contain a large quantity of it. It is 

* Whence the name of the acid, from the Latin malum. 



416 QURANIC CHEMISTRY. 

very soluble in water and alcohol, and crystallizes with diffi- 
culty ; its solution has a pleasant sour taste. This acid is 
bibasic. The malates of the alkaline metals are very soluble. 
The acid rnalate of ammonia (C 8 H 6 Oi ,NH 3 ) forms large 
transparent crystals ; the neutral malate of lead (C 8 H 4 Pb2O 10 ) 
is obtained as a white precipitate, which, if left for some time 
in a liquid containing free acid, changes into delicate crystals. 

814. When malic acid is heated to 350°, it is decomposed 
into water and two new acids, the maleic and fumaric, which 
are isomeric, and derived from the malic by the abstraction 
of the elements of water, C 8 H 6 O 10 — 2HO=C 8 H 4 8 . The 
maleic acid is obtained dissolved in the water, which distils 
over; it is crystallizable, and very soluble. This acid is 
identical with the equisetic acid obtained from different 
species of the Equisetum. When heated for some time to 
320°, it is converted into fvmaric acid ; this remains in the 
retort after the decomposition of maleic acid, and is also found 
in the fumitory, (Fumaria officinalis,) and in Iceland moss. 
It has the same composition as the maleic, and like it is bibasic, 
but is distinguished by being very sparingly soluble in cold 
water. 

815. Citric Acid, C 12 H 8 0i 4 . — This acid exists in the 
jtfices of many fruits, often associated with the tartaric and 
malic, and is the cause of the acid taste of the lemon. It is 
obtained by saturating lemon-juice with chalk, by which an 
insoluble citrate of lime is formed ; this is decomposed with 
an equivalent of sulphuric acid, which forms a sulphate of 
lime, and the citric acid is obtained by evaporation and crys- 
tallization. It forms large crystals pertaining to the trime- 
tric system ; it is very soluble in water, and has a strong but 
agreeable acid taste. The citric acid is tribasic, and forms 
with potash three salts, which are Ci 2 H 7 K0 14 , C, 2 H 6 K 2 14 , and 
C 12 H 5 K 3 0i 4 ; the first two are acids. The citrates are unim- 
portant. 

816. When the citric acid is exposed to heat in a retort, 
it evolves water, and it is converted into aconitic aci.d ; its 
composition is C I2 H 8 0i 4 — 2HO = C 12 H 6 ]2 . This acid is 
found combined with lime in the Acvnitum napellus ; it is 
tribasic, and very soluble in water. If, in the decomposition 
of citric acid, we carry the heat further, the aconitic acid is 
decomposed into carbonic acid gas and citraconic acid, 
0121160,2=2002+01011608. This last distils over as an oily 
fluid, which forms a crystalline mass on cooling. This acid 



VEGETABLE ACIDS. * 4-17 

is bibasic, and readily soluble in water ; when carefully 
heated it sublimes unchanged, but by a greater heat it is de- 
composed into water and a neutral liquid, called citraconide, 
C 10 H 4 O 6 . This slowly dissolves in water, and is converted 
into an acid, which is isomeric with the citraconic, though 
differing in its properties. 

817. Tannic Acid ; Tannin, C^H^O^. — The bark and 
leaves of many plants contain a peculiar substance, which is 
characterized by possessing an astringent taste, and by pre- 
cipitating gelatine from its solutions. This principle is abun- 
dant in the bark of many oaks, and in nut-galls, which are 
excrescences resulting from the puncture of an insect upon a 
species of oak. The infusion of oak-bark or nut-galls, pre- 
cipitates solutions of persalts of iron, of a bluish-black 
color. The vegetable extracts, kino and catechu, resemble 
the tannin of the oak, but differ in the color of their precipi- 
tates with solution of iron, and hence some chemists 
have considered them as distinct. It is, however, 
more probable that the tannin which they contain is 
identical with that of the oak, but modified in its reac- 
tions by the presence of other vegetable acids. Tan- 
nin is best obtained from gall-nuts, which yield 
thirty or forty per cent, by the following process. 
The gall-nuts in coarse powder are placed in the upper 
vessel represented in the figure, the mouth of which is 
previously stopped by a piece of linen. A quantity 
of washed ether (715) is then poured over them, 
which slowly filters through, and collects in the lower 
vessel, where it separates into two layers. The 
lower is an aqueous solution of pure tannic acid, 
while the lighter fluid is ether, holding in solution the 
coloring matter of the gall-nut and other impurities. 
The ether used in this process contains about one- 
twelfth part of water, which dissolves the tannic acid 
to the exclusion of all other substances. The solution of 
tannin is separated by means of a funnel, washed with a little 
ether, and finally evaporated in shallow vessels by a gentle 
heat. It forms a brilliant porous mass which has generally 
a light yellow tint ; it is very soluble in water, and the solu- 
tion has a purely astringent taste. The tannic acid is a feeble 
acid ; it dissolves the alkaline carbonates with effervescence. 
Its solution throws down insoluble compounds from solutions 
of nearly all the metallic salts, giving precipitates which are 



418 ORGANIC CHEMISTRY. 

often very characteristic ; with persalts of iron it yields a pur- 
plish-black, which is the basis of ordinary writing-ink and 
black dyes. With baryta it forms salts which are CaeH^BaO^ 
and 03611,4632024 ; it is therefore bibasic. 

818. This substance does not form an ether with alcohol 
like the other acids, and from many of its characters it seems 
to be more allied to sugar and gum, which, like it, have the 
power of neutralizing bases without possessing the other 
attributes of acids. 

Tannin is very liable to decomposition ; when a dilute so- 
lution is exposed to the air, it gradually absorbs oxygen and 
evolves carbonic acid gas, and is converted into gallic acid. 

819. Gallic Acid, C, 4 H 6 O 10 . — This is a product of the 
decomposition of tannin by exposure to the air, by the action 
of alkalies and acids, and by various ferments. It is best 
obtained by exposing a mixture of pulverized gall-nuts and 
water to the air, for two or three months in summer. A 
peculiar fermentation ensues, and the tannic is converted into 
gallic acid. It is readily dissolved out by boiling water, which 
deposits it on cooling in small silky crystals, which have an 
acid and astringent taste. It does not precipitate gelatine, 
and the black pergallate of iron loses its color when heated. 
This acid is bibasic, but its salts have been little studied. 
Gallic acid exists in large quantities in the fruit of the mango ; 
its formation from tannin is not well understood. 

Gallic acid dissolves in hot sulphuric acid, and on cooling 
the solution deposits a reddish brown crystalline powder called 
galleide ; it is gallic acid minus two equivalents of water. 

There are in addition to these many other vegetable acids, 
which are described in the larger works, but their characters 
have not generally been much studied. 

VOLATILE OR ESSENTIAL OILS. 

820. These terms are applied to a large class of products 
which are obtained by distilling plants with water, and they 
generally possess in a high degree the peculiar odor of the 
plants from which they are derived. They are very different 
in chemical characters ; some of those which contain oxygen, 
as the oils of meadow-sweet, bitter almonds, cumin, and cin- 
namon, have been already described ; and many others of 
less importance are analogous in their composition. 

821. Many of them consist of carbon and hydrogen only; 



VOLATILE OR ESSENTIAL OILS. 419 

and a large class which contain these elements in the ratio 
of eight to five, and combine directly with hydrochloric acid, 
are distinguished by the general name of camphene : of these 
the oil of turpentine is the most important; it is obtained by 
distillation from the crude turpentine, which exudes from 
many species of Pines, and is a colorless, aromatic liquid of 
a peculiar taste, having a specific gravity of -865, and boiling 
at 312°. It is of great use in the arts for the preparation of 
varnishes, and when carefully purified is employed for pur- 
poses of illumination under the names of camphene and pine 
oil. Its formula is C^H^. When dry hydrochloric acid is 
passed through the cooled oil, it is rapidly absorbed, and a 
white crystalline compound of the two separates from a liquid 
of the same composition as the solid. It contains the ele- 
ments of one equivalent of the oil and one of the acid ; the 
acid is so combined that it cannot be detected by the salts of 
silver, and we may regard this compound as the chlorinized 
species of a hydrocarbon, which is C 20 H 18 . It is volatile, and 
has a fragrant odor like camphor, and for this reason it was 
formerly called artificial camphor. 

822. When moist oil of turpentine is exposed to cold it 
often deposits crystals, which contain the elements of the oil 
plus four equivalents of water ; the same compound is 
slowly deposited from a mixture of the oil with nitric acid 
and alcohol. It forms colorless prismatic crystals, soluble 
in hot water and in alcohol ; its composition is C 20 H2o0 4 -f 
2aq ; the two equivalents of water are expelled by heat ; the 
name of terebol is given to this substance. 

823. Among the other oils included under the name of 
camphene, are those of juniper, pepper, caraway, parsley, 
citron, orange, lemon, and bergamot. All of these have 
the same boiling-point, and the same density of vapor as the 
oil of turpentine, and like it combine with hydrochloric acid 
to form solid or liquid compounds ; the oil of citron combines 
with two equivalents of the acid. Many of them yield 
terebol by the action of nitric acid and alcohol. The 
difference in the odor of these oils is quite unexplained ; it 
does not arise, as has been supposed, from the presence of 
an oxydized compound, for they may be distilled from 
hydrate of potash, or from potassium, without any other 
effect than that of refining the odor. The oil of roses is a 
carburet of hydrogen, probably C^H^. 

824. Many of the essential oils of both classes deposit 



420 ORGANIC CHEMISTRY. 

crystalline compounds when cooled ; they are often isomeric 
with the oxygenized oils, and sometimes are analogous to 
the terebol in their relations ; these bodies are designated as 
stearoptens or camphors, from their resemblance to common 
camphor. This last substance is a product of the Laurus 
camphora, and is obtained by distilling the wood of the tree 
with water. It is a light, volatile, and combustible solid, of 
a strong and fragrant odor. It is soluble in alcohol, but 
insoluble in water. Its formula is 02011,602. By long 
boiling with strong nitric acid, it is converted into camphoric 
acid, GjoHuA. 

825. Borneo Camphor. — This substance is obtained from 
the Dryabalanops camphor a of Borneo ; it is also found in 
the essential oil of valerian. It resembles the laurel cam- 
phor, but its odor is similar to that of pepper, and it has a 
pungent taste. It is very much valued in the East, and 
rarely reaches this country. Its formula is C2oH 18 2 ; when 
distilled with anhydrous phosphoric acid, it loses the elements 
of water, and yields a carbohydrogen, C^H^. This is called 
borneene, and occurs with the camphor in the Dryabalanops ; 
it is a camphene, and in contact with water gradually fixes 
the elements of two equivalents of that substance, and 
regenerates the camphor. Borneene exists in the essence of 
valerian, and the camphor which this last contains is formed 
only when the oil is moist. 

When this camphor is boiled with nitric acid, it loses 
two equivalents of hydrogen, and is converted into laurel 
camphor. 

826. Oil of Mustard. — The seed of black mustard, 
(Sinapis nigra,) when bruised with water and distilled, 
affords a pungent oil, which contains sulphur ; its formula is 
C 8 H 5 NS 2 ; with ammonia and other substances it affords many 
interesting products. When heated with potassium a decom- 
position ensues ; sulphocyanid of potassium is formed, and a 
fluid distils over, which is identical with the essential oil of 
garlic, as obtained when this plant is distilled with water. 
The reaction between these bodies is not definitely known. 
The essential oils of assaf&tida and many of the cruciferse, 
as horse-radish, radish, and cress, contain sulphur and are 
analogous to. the preceding. The odorant secretion of the 
Mephitis putorius, or pole-cat, contains a large amount of sul- 
phur, and is, perhaps, of the same class. 

827. Caoutchouc, Gum-Elastic. — This curious substance 




COLORING MATTERS. 4-21 

is found in the juices of many plants, but is principally ob- 
tained from the Hevea guia?iensis, and Iatropha elastica. Its 
ordinary properties are well known ; it is insoluble in water and 
alcohol, but dissolves in ether and many volatile hydrocar 
bons, of which the pure camphene is the best ; when softened 
by these solvents, it is wrought into a great variety of curious 
and useful articles. Small 
tubes of gum-elastic are very 
useful in the laboratory, to join 
glass-tubes, and form flexible 
joints, (381, Fig.) They are 
easily made from sheet caout- 
chouc by cutting the folded 
edges of the sheet with clean 
scissors over a glass tube, as seen in the figure. It is very 
combustible, and burns with a bright smoky flame. Caout- 
chouc is composed of carbon and hydrogen in equal equiva- 
lents, but as it is not volatile, and forms no compounds, its 
equivalent cannot be determined ; though, from the action of 
heat upon it, it is probably very high. When exposed to heat, 
it is decomposed and yields several volatile liquids which con- 
tain carbon and hydrogen in equal equivalents, and are con- 
sequently homologous with olefiant gas; among these is 
butyrene, C S H 8 , and two others, which are C 10 H, and C 40 H 40 . 
These mixed fluids are employed as a solvent for caoutchouc 
828. Gutta Percha is the product of a large tree called 
Percha, (pronounced pertcha,) found in the island of Singa- 
pore and adjacent parts, which, when felled and peeled, gives 
a milky juice, that being exposed to the air soon coagulates. 
It has lately been used in the arts as a substitute for caout 
chouc, which substance it much resembles in chemical proper 
ties. Submitted to analysis, it gave carbon 87-8, hydrogen 
12-2 ; while, according to Faraday, caoutchouc gave carbon 
87-2, hydrogen 12-8. Its action with solvents is the same as 
caoutchouc, but it is much less elastic. The specific gravity 
of gutta percha is 0-9791 ; that of caoutchouc 0-9355. 

COLORING MATTERS. 

Under this head may be conveniently described a number 
of bodies of vegetable and animal origin which are employed 
in the various processes of dyeing and coloring. But few 
36 



432 ORGANIC CHEMISTRY. 

of them have been accurately studied, and we shall men- 
tion only some of the more important. 

829. The yellow coloring matters of plants are gener- 
ally non-azotized substances. Among the most important, are 
quer citrine, the coloring principle of the Quercus tinctoria, 
and luteoline, from the woad, Reseda luteola, both of which 

, are soluble and crystalline. The yellows of turmeric and 
gamboge are of a resinous nature. Others employed in dye- 
ing are Morine, from the Morus tinctoria, and annatto. 

830. The red, coloring matters of alkanet and carthamus 
are insoluble in water, but dissolve in alkalies and are pre- 
cipitated by acids ; they appear to possess acid properties. 
The latter, carthamine, is the color of the pink saucers so 
much used in dyeing. The coloring principle of madder is 
called alizarine ; it is volatile, and forms orange-red crystals. 
Hematoxyline is obtained from log-wood ; it is very soluble, 
and forms yellow crystals ; its solution is reddened by acids, 
and rendered blue by alkalies. It gives a violet color with 
alum, and a black with persalts of iron. 

Carmine. — This substance is extracted from the insect 
called cochineal. When pure, it is a dark red crystalline 
powder, which contains nitrogen. The pigment known as 
carmine, is a compound of this principle with alumina. 

831. The green color of the leaves of plants is due to a 
substance called chlorophyle ; it somewhat resembles wax, 
and is soluble in alcohol, but insoluble in water. The blue 
color of flowers is very perishable, and has not been accu- 
rately examined. 

832. Coloring matters derived from the Lichens. — A 
number of plants of this class furnish beautiful blue and red 
coloring substances, which are used in dyeing, under the 
names of archil, cudbear, and litmus. These are derived 
from certain uncolored principles contained in the plants. 
Their nature may be understood from a description of one or 
two of these bodies. 

833. Lecanorine is obtained from a number of lichens ; 
it is a white crystalline body, which when boiled with water 
evolves carbonic acid, and is transformed into orcine. This 
forms large colorless crystals, which are volatile, have a sweet 
taste, and are very soluble in water ; its formula is C, 6 H 8 4 . 
When mixed with ammonia and exposed to the air, it absorbs 
oxygen and is converted into a deep red matter, which is a 
compound of ammonia with a new substance named orceine ; 
this is obtained by decomposing a solution of the ammoniacal 



INDIGO. 423 

compound with acetic acid, which precipitates it as a reddish 
brown powder. Its formula is C 16 H 9 N0 6 . 

834. Many other lichens contain substances which are 
very similar to lecanorine, and like it, produce fine red com- 
pounds. The bruised plants are mixed with water, lime, and 
an ammoniacal salt, when they undergo a kind of fermenta- 
tion, and generate the red substances. These colors are 
rendered blue by alkalies, but acids immediately restore the 
color. As the reddening of paper colored blue by an infusion 
of litmus is often referred to as a test of acidity, it is well to 
understand the principles upon which this reaction depends. 
In litmus the red of the orceine is changed to blue by the 
presence of lime. Any substance having a stronger affinity 
for the lime than the orceine has, will combine with it and 
restore the color. The neutral salts often redden litmus- 
paper ; sulphate of copper, for example, is decomposed by 
the lime of the litmus, forming sulphate of lime ; and as the 
oxyd of copper which is set free does not affect the orceine, 
the red color is restored precisely as if sulphuric acid had 
been employed. Test-papers prepared by an alcoholic infu- 
sion of purple dahlias, are very sensitive, turning green by 
the action of alkalies, remaining blue in neutral solutions, 
and becoming red in acids. 

INDIGO. 

835. This important coloring substance is obtained from a 
great number of plants, the principal of which are the Indigo- 
fera tinctoria and /. anil, with some species of the genera 
Isatis, Nerium, and Polygonum. The juices of these con- 
tain a peculiar colorless substance in solution, which, when 
exposed to the air, absorbs oxygen, and is converted into 
indigo. In the manufacture of this substance the plants are 
steeped in water, and made to undergo a kind of fermentation ; 
the clear liquid is then exposed to the air, and frequently 
agitated to facilitate the absorption of oxygen ; by this pro- 
cess it gradually becomes blue, and deposits the insoluble 
indigo. 

836. Commercial indigo is obtained in strongly cohering 
masses of a deep blue, which assume, when rubbed, a cop- 
pery metallic lustre. That of commerce is never pure, but 
is mixed with various foreign matters. Indigo is insoluble in 
water, alcohol, oils, dilute alkalies, and hydrochloric acid ; 
when cautiously heated it is volatilized in a purple vapor 



424 ORGANIC CHEMISTRY. 

which condenses in delicate crystals. The composition of 
indigo is expressed by Ci 6 H 5 N0 2 . 

In contact with water and deoxydizing agents, indigo is 
converted into a colorless substance, which is soluble in 
alkaline liquids ; this is generally effected by a mixture of 
lime and sulphate of iron ; one part of indigo in fine powder, 
four parts of quick lime, and three of protosulphate of iron, 
are digested with a large quantity of water. The pro- 
toxyd of iron formed by the action of the lime reduces the 
indigo, which in this form is dissolved by the alkaline 
solution, forming a yellow liquid. If this is exposed to the 
air, oxygen is absorbed, and the indigo is separated in its 
original color and insolubility. It is by impregnating cloth 
with this solution, and precipitating the indigo in its texture 
by the action of the air, that the fine indigo-blue colors are 
produced. 

837. Hydrochloric acid added to this yellow solution 
precipitates the dissolved substance as a gray crystalline 
powder, which, when moist, rapidly becomes blue by ab- 
sorbing oxygen, and is converted into indigo. It is called 
indigogene, and has the formula C 16 H 6 N0 2 ; by the addition 
of one equivalent of oxygen, it is converted into indigo and 
water, C, 6 H 6 N0 2 +0=HO + C 16 H 5 N0 2 . In its formation 
an equivalent of water is decomposed, its oxygen combining 
with the oxyd of iron. When indigo is mixed with a boiling 
alcoholic solution of caustic soda and grape sugar, it is con- 
verted into indigogene, while formic acid is produced by the 
oxydation of the sugar. This alcoholic solution, exposed to 
the air, deposits pure indigo in crystals. 

838. Concentrated sulphuric acid dissolves indigo, by the 
aid of a gentle heat, and forms two acids, (704,) which are 
formed by the couplement of one and two equivalents of 
indigo with one of sulphuric acid, the elements of two 
equivalents of water being eliminated. They are named the 
sulphindigotic, and sulphopurpuric acids. These acids and 
their salts are intensely blue. The first named is the most 
important; when a solution of sulphindigotic acid is boiled 
with woolen cloth, it is completely decolorized, the acid being 
taken up by the cloth : in this way the color called Saxon 
blue is obtained. It resists completely the action of water, 
but is easily dissolved out by a solution of the carbonate of 
ammonia, which distinguishes it from the blue color obtained 
with solutions t>f indigogene. 

839. When indigo in powder is heated with dilute nitric 



INDIGO. 425 

acid, it dissolves, forming a yellow solution, which affords 
by evaporation orange-red crystals of a new compound, 
called isatine. It forms beautiful rhombic prisms, which are 
sparingly soluble in cold water, but are readily dissolved by 
hot water and alcohol. It is derived from indigo by the addi- 
tion of two equivalents of oxygen, and its formula is 
C 16 H 5 N0 4 . When mixed with a solution of potash, it forms 
isatinic acid, which contains the elements of isatine plus one 
equivalent of water, and is decomposed by a gentle heat into 
these substances. With ammonia, isatine yields a variety 
of amides, which are derived from one, two, or three equiva- 
lents of isatine, by the action of one or more of ammonia. 

When isatine or indigo is distilled with the hydrate of pot- 
ash, carbonate of potash remains, while hydrogen gas is 
evolved, with a peculiar oily liquid, called anilene, which 
will be described among the organic alkaloids. Its formula 
is C 12 H 7 N. 

840. Indigo dissolves in a boiling concentrated solution of 
potash, and forms a yellow solution, which contains isatinate 
of potash ; but if the solution is evaporated and kept for 
some time in gentle fusion, hydrogen is disengaged, and a 
new salt, the anthranilate of potash, formed. The anthrani- 
lic acid has the composition C 14 H 7 N0 4 , and is derived from 
the elements of indigo and water thus, C 16 H 5 N0 2 + 6HO = 
C 14 H 7 N0 4 + 2C0 2 + 4H. Anthranilic acid crystallizes in 
colorless needles, and is soluble and volatile, but if mixed 
with sand or pounded glass and rapidly distilled, it is com- 
pletely resolved into carbonic acid and anilene, C 14 H 7 N0 4 = 
2C0 2 + C I2 H 7 N. 

841. The action of chlorine upon indigo or isatine yields 
two compounds called chlorisatine and bichlorisatine, in 
which chlorine replaces one and two equivalents of hydrogen. 
These substances closely resemble the normal isatine in their 
properties ; they yield acids similar to the isatine, and when 
distilled with hydrate of potash afford organic bases which 
correspond to anilene, in which one and two equivalents of 
chlorine replace hydrogen. 

By the action of hydrosulphuret of ammonia, isatine com- 
bines with one equivalent of hydrogen, and is converted into 
isatyde, C 16 H 6 N0 4 ; sulphureted hydrogen yields with isatine 
svlphisatine, C 16 H 6 N0 2 S 2 . A solution of potash removes the 
sulphur, and produces a rose-colored crystalline substance, 
indine, which is isomeric with indigogene. 

842. When indigo is boiled for some time with dilute nitric 
30* 



426 ORGANIC CHEMISTRY. 

acid it is converted into ammonia, carbonic acid, and anilic 
or nitrosalicylic acid, (762.) The reaction which produces 
salicylic acid is thus represented, Cj 6 H 5 N0 2 4-4HO-f-04= 
2C0 2 +NH 3 -fC 14 H 6 06. The prolonged action of nitric 
acid converts anilic acid into carbonic and nitrophenisic acids, 
(763.) 

The final product of the action of chlorine upon isatine is 
a volatile substance, crystallizing in golden yellow scales. 
It is called chloranile, and is C 12 C1 4 4 . This substance is 
also produced by the action of chlorine upon salicylic, anilic, 
and nitrophenisic acids, and many other bodies; it is easily 
prepared by boiling them with a dilute hydrochloric acid and 
chlorate of potash. 

ORGANIC BASES, OR ALKALOIDS. 

843. These names are employed to designate a class of 
bodies which, like ammonia, unite with acids and neutralize 
them, forming salts. This mode of combination is quite 
distinct from that of the metallic oxyds with the same acids ; 
these unite with the separation of the elements of water, 
while the salts of the organic alkaloids are formed by direct 
union, (677.) The alkaloids combine with metallic salts as 
well as with the acids themselves : for example, theine and 
strychnine combine with nitric acid, (NH0 6 ,) and with nitrate 
of silver, (NAgO fi ,) forming in both cases neutral crystalline 
compounds ; the hydrochlorates of the alkaloids unite with 
chlorid of platinum to form crystalline and sparingly soluble 
salts resembling the corresponding compound of sal am- 
moniac and platinum. 

All of the alkaloids contain nitrogen ; they may be con- 
veniently divided into those which are composed of carbon, 
hydrogen, and nitrogen only, and those that contain oxygen. 
The first are generally artificial products ; they are usually 
volatile, and, unless their equivalent is high, they are liquid 
at the ordinary temperature. The second class, which in- 
cludes the larger number, are generally products of vegetable 
life, and constitute the active medicinal principles of the 
plants which contain them. They have generally a powerful 
action upon the animal economy; the volatile alkaloids of the 
first class are also active poisons. Some artificial organic 
bases have been produced which contain sulphur and sele- 
nium, replacing oxygen ; chlorine, bromine, and the residue 
of nitric acid may also be substituted for hydrogen in the 



ORGANIC BASES, OH ALKALOIDS. 427 

constitution of these bodies. The limits of this work will 
permit us to notice only some of the more important alkaloids 
of the above classes. 

844. Anilene, C 12 H 7 N. — The production of this base has 
been already described, when speaking of indigo and its 
derivatives. Another curious process for its production has 
been lately discovered by M. Hoffman : when nitrobenzene, 
(757,) C12H4NO4, is dissolved in alcohol with a little sulphuric 
acid, and fragments of iron or zinc are added to the mixture, 
the nascent hydrogen arising from the solution of the metal 
converts the nitrobenzene into anilene and water, C 12 H 4 N0 4 
+ 7H = 4HO -f- C 12 H 7 N. The same change is produced 
when sulphureted hydrogen gas is passed through an alco- 
holic solution of nitrobenzene previously saturated with 
ammonia. The gas is decomposed, and sulphur separates 
in a crystalline form, while anilene remains in solution. 
Anilene is also found in the oil of coal-tar. It is a colorless, 
oily liquid, which boils at 328°, and has a density of 1-028 ; 
it has a pleasant vinous odor, and burning taste, and is 
highly poisonous. When mixed with a solution of bleaching 
powder, (hypochlorite of lime,) a deep violet-blue color is 
produced, which enables us to detect the smallest trace of 
this alkaloid. Anilene is a strong base, and decomposes the 
salts of zinc and iron, precipitating their hydrated oxyds ; its 
salts crystallize beautifully. When the oxalate of anilene is 
exposed to heat, it loses the elements of water, and is con- 
verted into oxanilide, which corresponds precisely to oxa- 
mide, (698,) and by the action of alkalies and acids 
regenerates oxalic acid and anilene. The other salts of 
anilene form similar compounds, which are quite analogous 
to the amides, and are designated by the name of anilides. 

845. The formation of ckloranilene, C 12 (H 6 C1) N, and 
bichlor anilene, C 12 (H 5 CI 2 )N, with the corresponding bro- 
mine compounds, has been already alluded to. They are 
crystalline solids and act as bases, but less energetically than 
anilene. Binitrobenzene, which may be regarded as nitroben- 
zene, in which two more equivalents of hydrogen have been 
replaced by the residue of nitric acid, NH0 6 — 2 , yields by 
the action of sulphureted hydrogen fine yellow prisms of a 
new organic base, named nitraniline, which is C 12 H 6 N 2 4 
anilene, in which NH0 4 replaces H 2 , thus C 12 (H 4 ,NH0 4 )N. 
The final product of strong nitric acid upon anilene, is nitro- 
phenisic acid ; with a mixture of chlorate of potash and 
hydrochloric acid it forms chloranile. 



428 ORGANIC CHEMISTRY. 

846. Quinoline, C 18 H 7 N. — This base is formed when the 
oxygenized alkaloids cinchonine, quinine, or strychnine are 
distilled with hydrate of potash ; thus, one equivalent of 
quinine, 0^^204 + 4HO=2C 18 H 7 N + 4C0 2 +14H. It is 
identical with the alkaloid which is associated with anilene in 
coal-tar, and which has been described under the name of 
leukol. Quinoline is an oily liquid, with a powerful odor, 
and is very poisonous. 

847. Nicotine, Cj H 7 N. — This alkaloid is obtained by dis- 
tilling a concentrated infusion of tobacco with lime or hydrate 
of potash. The recent plant contains a peculiar crystalline 
body, called nicotianine, which affords nicotine by the action 
of caustic potash, but it is probable that in the prepared 
tobacco nicotine exists ready formed. When tobacco is 
smoked in a German pipe, the liquid which condenses in 
the long stem, contains a large quantity of this alkaloid. 
Nicotine is an oily liquid, heavier than water ; it has a burn 
ing taste, with the odor of tobacco, and is an active poison. 

848. Conine, Ci 6 H 15 N. — This base exists in all parts of 
the Conium maculatum, but most abundantly in the seeds ; it 
is extracted by distilling the infusion with a dilute solution of 
potash. Like the preceding bodies, it is an oily liquid, 
which possesses strong alkaline properties. It has a disa- 
greeable taste and odor, and is very poisonous, possessing in a 
high degree the medicinal powers of the conium. 

849. Amarine or Benzoline, C 42 H, 8 N 2 . — When hydroben- 
zamide, (754,) is boiled with a dilute solution of potash 
it dissolves, and on cooling, crystals of amarine (benzo- 
line of Fownes) separate. It has the same composition and 
the same equivalent as the hydrobenzamide, but is a strong 
base. The same alkaloid is formed by the action of ammo- 
nia upon an alcoholic solution of bitter almond oil. 

By a similar process to that by which nitrobenzene yields 
anilene, many nitric species of hydrocarbons afford peculiar 
bases, which, like the preceding, contain one equivalent of 
hydrogen and no oxygen. 

850. Alkaloids of Cinchona, or Peruvian Bark. — The 
barks of several species of cinchona owe their medicinal 
properties to the presence of two alkaloids which are named 
quinine and cinchonine. They are extracted by digesting 
the bark in dilute acid, and adding to the infusion a solution 
of carbonate of soda, which precipitates the alkaloids in an 
impure state. The precipitate is washed and dissolved in 



ORGANIC BASES, OR ALKALOIDS. 429 

boiling alcohol ; a little animal charcoal is added to remove 
some coloring matter, and the filtered liquid, on cooling, de- 
posits crystals of cinchonine, while the more soluble quinine 
is obtained by evaporation. Quinine is a white crystalline 
substance, sparingly soluble in water, but readily so in 
alcohol and ether. It dissolves in acids, and forms with them 
crystallizable salts, which are very bitter. The sulphate and 
hydrochlorate are much employed in medicine. The formula 
for this alkaloid is C 40 H 24 N 2 O 4 . Cinchonine resembles quinine 
in its properties, but is less soluble in alcohol and ether ; like 
that alkaloid it is employed as a febrifuge. Its composition 
is C^H^NzC^, differing from quinine only by two equivalents 
of oxygen. 

In addition to these, two other alkaloids, aricine andi 
cinchoratine, have been observed in different species of cin- 
chona, but they are little known. The alkaloids in cinchona 
bark are combined with a peculiar bibasic acid called the 
kinic ; its composition is C 14 H I2 12 . 

851. Alkaloids of Opium. — This substance is the inspis- 
sated juice of the capsules of a species of poppy, Papaver 
somniferum, and contains several organic bases. The most 
important of these, and the one to which it owes its power as 
an anodyne, is morphine. It is prepared by precipitating a 
solution of opium by carbonate of soda, as in the process foi 
quinine ; the impure morphine is digested in cold alcohol to 
remove some other alkaloids present, and finally dissolved m 
dilute acetic acid. The cautious addition of ammonia to the 
acetate thus formed, precipitates the morphine, which is dis- 
solved in hot alcohol, and crystallizes on cooling. It forms 
brilliant rectangular prisms, which are sparingly soluble in 
water, readily so in hot alcohol, and insoluble in ether; it 
has a persistent bitter taste. Its formula is C^H^NO. 
Morphine forms crystalline salts, some of which, as the 
hydrochlorate, sulphate, and acetate, are much employed in 
medicine. The best opium contains six or eight per cent, of 
this alkaloid. 

852. Codeine is a base which occurs in small quantities 
with morphine ; it is more soluble in Water than that alkaloid, 
and dissolves readily in ether. It seems allied to morphine 
in its effects upon the animal system. The composition of 
codeine is C 36 H 2 ,N0 6 . 

Narcotine. — This alkaloid is found in considerable quan- 
tities in opium ; it is separated from the preceding by being 



430 ORGANIC CHEMISTRY. 

very soluble in ether, and insoluble in water. It is a feeble 
base; the formula of narcotine is C 46 H 25 N0 14 . When heated 
with a mixture of sulphuric acid and peroxyd of manganese, 
it combines with four equivalents of oxygen, and is decom- 
posed into a peculiar nonazotized acid called the opianic, and 
a new alkaloid, cotarnine, which is C^HigNOe. 

In addition to those already mentioned, opium contains 
three other bases in small quantity ; they are named thebaine, 
pseudomorphine, and narceine ; but little is known of them. 
It affords also a peculiar tribasic acid which is called the 
meconic ; its formula is Ci 4 H 4 14 ; the morphia exists in the 
juice of the poppy combined with meconic and sulphuric 
acids. 

853. Strychnine. — This alkaloid is found in the Strychnos 
nux-vomica, and several other plants of the same genus. It 
is prepared by digesting the nux-vomica with water acidulated 
by sulphuric acid, and precipitating the solution by caustic 
lime. The impure precipitate is boiled with alcohol and 
animal charcoal, and the liquid on cooling deposits the strych- 
nine in crystals. It is almost insoluble in water, absolute 
alcohol, and ether, but dissolves in dilute alcohol ; its salts 
are intensely bitter and highly poisonous. Strychnine and 
its compounds produce a spasmodic affection of the muscles 
of voluntary motion in cases of paralysis ; they are used in 
minute doses with great benefit. The poison of the celebrated 
Upas is the product of the Strychnos tieute, and owes 
its activity to strychnine. The formula for strychnine is 
C 44 H 24 N 2 4 ; when fused with hydrate of potash it yields 
quinoleine. Brucine is another organic base which is asso- 
ciated with the last in several species of Strychnos ; it re- 
sembles it in its characters, but is somewhat less active as a 
poison. 

854. Solanine, from the Solanum nigrum, and several 
other species, Hyoscyamine, from Hyoscyamus niger, 
Atropine, from Atropa belladonna, and Daturine, from 
Datura stramonium, are alkaline principles which possess in 
great perfection the poisonous properties of the plants from 
which they are derived. They are obtained by somewhat 
complicated processes, and are crystalline and volatile. Their 
salts are employed in medicine. 

855. Veratrine is found in the Veratrum album, and 
some other species of the same genus ; it forms a white 
crystalline powder, which is insoluble in water, but soluble 



OTHER VEGETABLE PRINCIPLES. 431 

in alcohol. It is a powerful acrid poison, but is used 
medicinally in neuralgia with beneficial results. Aconitine 
is obtained from the Aconitum napellus, and resembles 
veratrine in its properties. Sanguinarine is an alkaloid 
which exists in the blood-root, Sanguinaria canadensis, and 
to which this plant owes its active properties. Emetine, the 
emetic principle of ipecacuana, and capsicine, to which the 
pungency of cayenne pepper is due, are also organic bases. 

856. Theine ; Caffeine, C, 6 H 10 N 4 O 4 . — This organic base 
is found in coffee, tea, the fruit of the Paulinia so rbalis, and 
the Ilex paraguayensis, which affords the matte, or 
Paraguay tea. It is most abundant in green tea, which 
contains from two to five per cent. ; the best coffee does not 
yield one per cent. To obtain it, a strong decoction of the 
leaves is mixed with a solution of the surbasic acetate of 
lead, as long as a precipitate is formed ; to the clear solution 
a little ammonia is added, to precipitate the excess of lead, 
and the liquid by evaporation furnishes theine in delicate 
silky crystals. It is readily soluble in hot water and alcohol, 
and may be volatilized without decomposition ; its taste is 
slightly bitter. Theine is a feeble base, and its salts are 
easily decomposed ; the hydrochlorate crystallizes beautifully. 

857. It is worthy of notice, that the plants which furnish 
this alkaloid are used by different nations to prepare a 
grateful and gently stimulating beverage. As these sub- 
stances resemble each other only in containing theine, it is 
probable that they owe their common properties to the 
presence of this principle, and that, in some unknown 
manner, it promotes digestion and the other vital functions. 
The Brazilians prepare from the 4 fruit of the Paulinia 
sorbalis an extract called by them guarana, which is 
much esteemed as a remedy in dysentery and nephritic, 
complaints ; it contains a considerable quantity of theine. 

The seeds of cocoa, Tlieobroma cacao, contain a crystal- 
line substance, somewhat analogous to theine. It is called 
tJueobromine, and has the formula C 18 Hi N 6 O 4 . It possesses 
feebly basic powers. 

OTHER VEGETABLE PRINCIPLES. 

858. Besides those already described under the previous 
heads, there are a great number of neutral crystalline prin- 
ciples which have been extracted from vegetables. Among 



432 ORGANIC CHEMISTRY. 

them are a few whose reactions have been studied, that 
exhibit a remarkable tendency to decomposition, under the 
influence of ferments and other agents. Under this class 
may be included amygdaline, asparagine, salicine, and phlo- 
ridzine. 

859. Amygdaline. — This principle is contained in bitter 
almonds, and peach kernels. It is prepared by pressing the 
bruised almonds between heated plates to separate the fat oil, 
and boiling the residue in strong alcohol. The alcohol is then 
distilled off in a water-bath, and the syrupy residue mixed 
with a little yeast is set aside to ferment ; by this treatment 
a portion of sugar which the almonds contain is destroyed. 
The clear liquid is again evaporated to a syrup and mixed 
with ether, which precipitates the amygdaline in a crystalline 
powder. It is readily soluble in alcohol and water, and 
crystallizes from the latter solvent in large prisms, with six 
equivalents of water ; it has a bitter taste. The formula of 
amygdaline is C 40 H 27 NO 2 2 ; when boiled with water of baryta, 
it takes up the elements of two equivalents of water, and is 
converted into ammonia and amygdalic acid, which remains 
dissolved as amygdalate of baryta ; its formula is C^H^O^. 
Amygdaline may be regarded as the amide of this peculiar 
acid. 

This principle exists in bitter almonds, in the proportion 
of four or five per cent. ; besides this, they contain an 
albuminous matter, which, has some analogy to animal 
albumen, and it is called emulsine, or synaptase ; it consti- 
tutes the great part of sweet almonds, which contain no 
amygdaline. When a solution of amygdaline is mixed with 
about one-tenth part of emulsine, a decomposition ensues, and 
in a few minutes the amygdaline is completely converted into 
benzoilol, prussic acid and grape sugar. One equivalent of 
amygdaline and four of water, contain the elements of one 
equivalent of benzoilol, one of prussic acid, and two of grape 
sugar, C^NQa-MHO == C 14 H 6 2 + C 2 HN + 2C 12 H 12 12 . 
The action of emulsine in this singular decomposition, is analo- 
gous to that of a ferment ; if exposed to a heat of 212°, it 
coagulates, becomes insoluble, and loses the power of effect- 
ing the change. 

860. Asparagine. — This substance is found in the stalks 
of asparagus, the roots of marsh-mallows, beets, and many 
other plants, and separates in a crystalline form from the 
concentrated juice or decoction. It crystallizes in transparent 



OTHER VEGETABLE PRINCIPLES. ** 433 

rhombic prisms, of a fresh and somewhat nauseous taste; it 
is, sparingly soluble in cold, but more readily in boiling water. 
The formula for asparagine is C 8 H 8 N 2 6 . Asparagine is the 
amide of a peculiar acid galled the aspartic ; by the action 
of dilute alkalies or acids it assumes the elements of water, 
and yields aspartic acid and ammonia, C 8 H 8 N 2 6 -f 2HO= 
C 8 H 7 N0 8 +NH 3 . The aspartic acid is cry stall izable and 
sparingly soluble in water; it is an acid amide, (697.) 
When boiled for some time with hydrochloric acid or a 
solution of potash, it is converted into ammonia and a new 
acid which has not yet been examined. When a solution of 
impure asparagine is exposed to the air it undergoes a kind 
of fermentation, and after some time the liquid contains 
nothing but neutral succinate of ammonia. An equivalent 
of asparagine with four of water contains the elements of 
one equivalent of the succinate of ammonia, and two of 
oxygen ; but the reaction is not understood, and is probably 
more complex. 

861. Salicine. — This principle exists in the bark of those 
species of willow which have a bitter taste. The decoction 
of the bark is mixed with the surbasic acetate of lead as long 
as a precipitate is formed ; to the filtered liquid dilute sul- 
phuric acid is added to precipitate the dissolved lead, carefully 
avoiding an excess. The solution is then decolorized by 
animal charcoal, and, by evaporation and cooling, deposits 
pure salicine. It is so abundant in the bark of some willows 
as to separate in crystals when a concentrated decoction is 
cooled. Salicine forms small white crystals, readily soluble 
in alcohol and water ; it has a very bitter taste, and is em- 
ployed in medicine as a febrifuge and tonic. Its formula is 
CagHjaOw. 

862. When a solution of salicine is mixed with a portion 
of the emulsine of sweet almonds, and exposed for some 
hours to a heat of 105° F., it is completely decomposed into 
grape sugar and a new compound, saligenine, which sepa- 
rates in fine rhombohedral crystals. Its composition is repre- 
sented by C 14 H 8 4 . One equivalent of salicine and two of 
water contain the elements of one equivalent of grape sugar 
and one of saligenine, C 26 H 18 14 + 2HO=CuH 12 12 + C 14 H fe 4 . 
Saligenine is readily soluble in water, alcohol, and ether; 
dilute acids convert it into a white insoluble matter which is 
named saliretine, which is formed from it by the loss of the 
elements of two equivalents of water. When a solution of 

37 



434 ORGANIC CHEMISTRY. 

saligenine is mixed with chromic acid it loses two equivalents 
of hydrogen and is converted into salicylol, (759 ;) the same 
change is effected by oxyd of silver, which is reduced to the 
metallic state. • 

863. When a solution of salicine in dilute sulphuric or 
hydrochloric acid is heated, it is first decomposed into grape 
sugar and saligenine, but the farther action of the acid con- 
verts the latter into saliretine, which separates in white flakes. 

A mixture of salicine with dilute sulphuric acid and bichro- 
mate of potash affords, by distillation, a large quantity of 
salicylol. Boiling dilute nitric acid decomposes it ; first con- 
verting the saligenine into salicylol, and then into nitro- 
salicylic acid ; if the acid is concentrated the final product is 
the nitrophenisic acid, accompanied with oxalic acid formed 
from the sugar. A mixture of hydrochloric acid and chlorate 
of potash converts it into chloranile ; when fused with 
potash, salicine yields a large quantity of salicylic acid. 

864. If salicine is dissolved in cold, very dilute nitric 
acid, it gradually deposits crystals of a new substance called 
helicine. Its composition is expressed by C^H^O^, and it is 
formed from salicine by the addition of two equivalents of 
oxygen, and the separation of one of water. Under the 
influence of emulsine, it takes up the elements of one 
equivalent of water, and is resolved into grape sugar and 
salicylol, C2 6 H 17 15 + HO=C 14 H 6 4 + C,2H 12 12 ; dilute acids 
cause the same decomposition. 

865. Phloridzine. — /This principle is found in the root- 
bark of the apple, pear, cherry, and some other trees. A 
concentrated decoction of the apple root-bark deposits, by 
cooling, a brown crystalline powder, which may be de- 
colorized by animal charcoal. It forms delicate silky 
crystals, which are almost insoluble in cold water, but 
readily soluble in hot water and alcohol. It is bitter, and a 
febrifuge, and has been employed medicinally. The com- 
position of phloridzine may be expressed by C^HwO^ + Saq. 
If boiled with dilute acids it is converted into grape sugar, 
and an insoluble compound called phloretine, C24Hi 4 0, 2 + 
4HO=C 12 H 12 12 +C 12 H 6 4 . 

When phloridzine is exposed to the action of moist air 
and ammonia, it is gradually changed into a very soluble 
blue compound. From the solution of this, acetic acid pre- 
cipitates a red powder called phloridzeine y which dissolves in 
ammonia with a splendid blue color. It is derived from 




THE CYAN1DS, AND COMPOUNDS DERIVED FROM THEM. 435 

phloridzine, by the addition of the elements of one equivalent 
of ammonia and four of oxygen, with the separation of one 
of water. This reaction is analogous to that by which 
orceine is formed from orcine, (830.) 



THE CYANIDS, AND THE COMPOUNDS DERIVED FROM THEM. 

866. The cyanids do not exist in nature, but are ex- 
clusively artificial products. When any organic substance 
containing nitrogen is heated with potassium, a cyanid of 
potassium is formed, and the same result is obtained if 
caustic potash is used, provided this is not in excess. If 
nitrogen gas is passed over a mixture of carbonate of potash 
and charcoal heated to bright redness, it is absorbed, and a 
cyanid is formed ; the same result is afforded by ammonia. 
The formula of cyanid of potassium is C 2 KN, and it may 
hence be formed from the direct union of the potassium 
reduced by the carbon, with the nitrogen and carbon present. 

867. Hydrocyanic Acid; Prussic Acid, C 2 HN. — This 
acid is obtained by distilling cyanid of potassium with dilute 
sulphuric acid ; but a more elegant process is to decompose 
cyanid of mercury by sulphureted hydrogen, C 2 HgN + HS 
= HgS-fC 2 HN. The reaction is aided by a gentle heat, 
and the pure acid distils over ; it must be collected in a 
cool receiver. Hydrocyanic acid is a colorless, limpid liquid, 
which has a specific gravity of '697, and boils at 80°. It is 
very combustible, and burns with a white flame ; it scarcely 
reddens litmus paper. The taste of this substance is pungent 
and disagreeable, and its odor very powerful, recalling that 
of peach blossoms or bitter almonds : the latter owe a 
portion of their peculiar flavor to this acid, which, as has 
been before stated, is one of the products of the decom- 
position of amygdaline by emulsine, and constitutes a part 
of the crude bitter almond oil. 

868. Hydrocyanic acid is one of the most fatal poisons 
known ; a single drop of the pure acid, placed upon the 
tongue of a large dog, produces immediate insensibility and 
death ; and the diluted acid in even very small doses, causes 
giddiness, often followed by nausea. It appears to act as a 
sedative to the arterial system, and the suspension of anima- 
tion following a poisonous dose of it, does not always result 
in death if proper stimulants are employed ; ammonia is 
generally considered as the most efficient antidote to its effects. 



436 ORGANIC CHEMISTRY. 

The vapor of the concentrated acid is very poisonous, but when 
considerably diluted with air, does not appear to be so dele- 
terious as has been generally supposed. In the process of 
the arts, it is frequently evolved in considerable quantities, 
yet the workmen who are constantly exposed to it, experience 
no injurious effects. The diluted acid is much employed in 
medicine. When pure it soon decomposes spontaneously ; 
but if diluted, and especially if a small quantity of sulphuric 
acid is present, it may be preserved for a long time. 

869. When the vapor of formiate of ammonia is passed 
through a tube heated to 400°, it is completely decomposed 
into prussic acid and water, C 2 H 2 4 ,NH 3 =4HO-f C 2 HN. 
The cyanids, in the presence of a strong acid, take up again 
the elements of water, and regenerate formic acid and ammo- 
nia ; alkalies cause the same decomposition ; a solution of 
cyanid of potassium is decomposed by boiling. Ammonia is 
evolved, and formiate of potash is formed. Hydrocyanic 
acid is then to be regarded as an amide of formic acid, 
differing from the ordinary amides of monobasic acids in 
being formed by the abstraction of four equivalents of water. 
With metallic oxyds, hydrocyanic acid yields cyanids and 
water. 

870. Cyanid of Potassium. — This is formed by the action 
of potash upon animal matters, but in this way is always im- 
pure. It is obtained pure by saturating an alcoholic solution 
of potash with hydrocyanic acid, or by decomposing the ferro- 
cyanid. This salt, well known in the arts as yellow prussiate 
of potash, contains the elements of two equivalents of cyanid 
of potassium and one of cyanid of iron. When it is heated 
to redness in a close vessel, the cyanid of iron is decomposed 
into nitrogen and a carburet of iron, and pure cyanid of potas- 
sium remains; the mass is boiled with alcohol, which deposits 
the cyanid on cooling, in cubical crystals. It is very soluble 
and deliquescent, and has an alkaline reaction. Its taste is 
caustic, at the same time resembling that of prussic acid, and 
it is highly poisonous. Its aqueous solution smells of hydro- 
cyanic acid ; it cannot be kept in this state, as it is gradually 
converted into formiate of potash, with the evolution of 
ammonia. 

The cyanid of potassium is of great use in chemical 
analysis, particularly as a reducing agent, in which it is 
inferior only to potassium ; if the cyanid is fused in a cruci- 
ble, and oxyd of copper is added to it, the latter is reduced 



THE CYANIDS, AND COMPOUNDS DERIVED FROM THEM. 437 

with ignition ; the oxyds of lead and iron, and even their sul- 
phurets are reduced in the same way, at a temperature below 
redness. 

871. The cyanids of the metals are generally insoluble in 
water, but soluble in an excess of cyanid of potassium. 
The cyanid of mercury, C 2 HgN, is, however, soluble and 
crystallizable. It is formed by boiling two parts of the 
yellow prussiate of potash with three of sulphate of mer- 
cury in fifteen of water for a few minutes ; on cooling the 
cyanid crystallizes. It is readily soluble in water and alco- 
hol, has a nauseous metallic taste, and is very poisonous. 
The cyanid of silver, C 2 AgN, is a white insoluble precipitate, 
resembling the chlorid. 

The action of chlorine upon hydrocyanic acid or cyanid 
of mercury yields a gaseous compound, in which chlorine 
replaces the hydrogen. Its composition is C 2 CIN. This 
gas has a pungent and disagreeable odor, and is absorbed by 
water without decomposition. The action of bromine and 
iodine upon the cyanid of mercury yields crystalline com- 
pounds which correspond to the last. They are volatile and 
poisonous. These substances are generally described as 
chlorid, bromid, and iodid of cyanogen. 

872. Cyanogen. — When cyanid of mercury is heated 
nearly to redness, it is decomposed into metallic mercury and a 
colorless inflammable gas, to which the name of cyanogen is 
given. The decomposition is very simple, C 2 HgN==Hg + 
C 2 N. This gas has a pungent odor, resembling that of 
prussic acid, and burns with a very rich purple violet flame, 
yielding carbonic acid and nitrogen. It is soluble in water 
and alcohol, and for this reason must be collected over mer- 
cury. Its density is 1-8026, and it is composed of two 
equivalents, or one volume of carbon vapor, and one volume 
of nitrogen, condensed into one volume, 8320 + '9-706 = 
1-8026, or one volume of cyanogen. 

When potassium is heated in cyanogen gas, union takes 
place with the evolution of heat and light, and cyanid of 
potassium is formed. Many chemists regard cyanogen as 
allied to chlorine in its characters and possessing, although a 
compound, the reactions of an element. The cyanid of po- 
tassium is upon this view assimilated to the chlorid of the 
same metal, and the prussic acid is considered as a compound 
of cyanogen with hydrogen, analogous to hydrochloric acid. 
These two bodies will not, however, combine under anv cir- 
37* 



438 ORGANIC CHEMISTRY. 

cumstances, nor does cyanogen act upon organic bodies 
replacing their hydrogen, so that the analogies by which this 
theory is supported are but very imperfect. 

873. When cyanogen unites directly with sulphureted 
hydrogen, its equivalent is represented by two volumes, so 
that its formula must be doubled, and the real composition of 
the gas is hence C 4 N 2 . 

Hydrocyanic acid and the cyanids react upon many or- 
ganic matters which contain oxygen or chlorine ; the hydro- 
gen or metal unites with these, substituting in their places the 
residue C 2 N. Thus hydrochloric ether, C 4 H 6 C1 + C 2 KN = 
KC1 + C 4 H 5 C 2 N, or C 6 H 3 N ; these compounds are bu-t little 
known. 

CYANATES. 

874. These salts are formed by the direct oxydation of 
the cyanids ; when oxyd of lead is added to fused cyanid of 
potassium, the metal is reduced, and cyanate of potash is 
formed, C 2 KN + 2PbO=2Pb + C 2 KN0 2 . The cyanic acid, 
C 2 HN0 2 , cannot be obtained from the cyanates by a stronger 
acid, as it immediately combines with the elements of water 
and is resolved into carbonic acid and ammonia, C 2 HN0 2 -f 
2HO=2C0 2 -f NH 3 . The aqueous solution of the cyanate 
of potash undergoes the same decomposition, spontaneously 
evolving ammonia and leaving bicarbonate of potash. Cyanic 
acid may hence be viewed as an amide of carbonic acid. 

875. Cyanic acid is obtained by the dry distillation of 
cyanuric acid, which is polymeric of it, and contains the 
elements of three equivalents ; the product is condensed in a 
carefully cooled receiver, and is a colorless liquid of a pene- 
trating odor, resembling the acetic acid ; it is very corrosive 
to the skin, and causes vesication as effectually as a hot iron. 
It cannot be preserved for any considerable time, but changes 
into a white insoluble mass like porcelain, which is called 
cyamelide, and has the same composition as the acid ; but 
its real nature is not known ; by heat it is converted again 
into cyanic acid. 

876. Cyanate of Potash, C 2 KN0 2 , is prepared from the 
cyanid as before described, or more cheaply from the yellow 
prussiate of potash. This is carefully dried at 212°, mixed 
with one-half its weight of peroxyd of manganese, and 
heated to low redness ; the mass takes lire and burns like 
tinder; the residue contains cyanate of potash, which may 



CYANATES. 439 

be extracted by boiling alcohol ; from this solution it crys- 
tallizes on cooling. The cyanate of potash crystallizes in 
tables resembling chlorate of potash ; it is very soluble in 
water, but the solution slowly decomposes into carbonate of 
potash and ammonia, and the crystals undergo the same 
change in moist air. 

877. The vapor of cyanic acid combines withthe same 
monia and forms a crystalline compound, which is C 2 HN0 2 , 
2NH 3 . This is readily soluble in water, and possesses the 
characters of a cyanate; if the solution is boiled, one 
equivalent of ammonia is expelled, and there remain the 
elements of the neutral cyanate, C 2 HN0 2 ,NH 3 , but by 
evaporation crystals of a new substance are deposited, which 
lias none of the characters of a salt. It contains the 
elements of cyanate of ammonia, but, unlike the cyanates, 
unites directly with the acids to form definite compounds. 
This singular substance is contained in large quantities in 
urine, and is hence named urea. It is obtained by evapo- 
rating fresh human urine at a heat below 212° to a small 
bulk, and mixing the residue with nitric acid. The nitrate 
of urea, which is sparingly soluble in dilute nitric acid, 
separates in pearly plates, which are washed in cold water 
and decomposed by carbonate of potash. The nitrate of 
potash is separated by crystallization from the more soluble 
urea, which is finally purified by crystallizing it from 
alcohol. 

878. A better process is to decompose the cyanate of 
potash by a salt of ammonia ; twenty-eight parts of dried 
prussiate of potash are roasted with oxyd of manganese as 
before described, and the cyanate, dissolved from the mass 
by washing with cold water, is mixed with twenty-and-a- 
half parts of dry sulphate of ammonia, and the whole 
evaporated to dryness in a water-bath. Sulphate of potash 
and cyanate of ammonia are first formed, and this last is 
immediately changed into urea ; the dry mass is boiled with 
alcohol, which dissolves the urea, and on cooling deposits 
it in crystals. 

879. Urea forms transparent, colorless, four-sided prisms, 
readily soluble in water and alcohol ; it is inodorous, and its 
taste is fresh and biting, resembling that of nitre. The basic 
powers of urea are very weak, but it yields crystalline com- 
pounds with hydrochloric, nitric, and oxalic acids. The 
nitrate, C 2 H 4 N 2 2 ,NH0 6 , forms large brilliant plates, which 






440 ORGANIC CHEMISTRY. 

require eight parts of water for solution. When a solution 
of urea is evaporated with one of nitrate of silver, the 
elements re-arrange themselves to form nitrate of ammonia 
and cyanate of silver. 

SULPHOCYANATES. 

880. These compounds are cyanates in which the oxygen 
is replaced by sulphur, and are much more stable than the 
previous class. When cyanid of potassium is fused with a 
metallic sulphuret or with sulphur, it combines with two 
equivalents and forms sulphocyanate of potash, C 2 KNS 2 . 
The sulphocyanic acid, C 2 HNS 2 , is obtained by decomposing 
the sulphocyanate of lead by sulphuric acid, and is a color- 
less, sour liquid, with an odor like vinegar. It is not poison- 
ous. The sulphocyanate of potash is prepared by fusing 
in an iron vessel a mixture of forty-six parts of dry prussiate of 
potash, seventeen of dry carbonate of potash, and thirty-two 
of sulphur. The vessel is kept covered, and the mixture 
occasionally stirred until the evolution of gas has ceased, and 
the heat, which should be gentle at first, has been raised to 
redness. The sulphocyanate is dissolved out of the black 
mass by boiling water, and crystallizes by evaporation and 
cooling. It forms colorless prismatic crystals of a sharp, 
cooling taste, like nitre. It is deliquescent, and very soluble 
in water and alcohol. When its solution is heated with 
nitric acid, and chlorine gas is passed through it, a yellow 
precipitate is formed, which was formerly regarded as a 
sulphuret of cyanogen, but it contains oxygen and hydrogen, 
and its composition varies exceedingly. The name of 
cyanox sulphide has been given to it ; when exposed to heat 
it evolves sulphur, sulphuret of carbon, and several other 
compounds, and leaves a grayish yellow residue which 
Liebig has named mellon. Its composition is C 6 N 4 ; when 
exposed to a bright red heat, it is resolved into cyanogen and 
nitrogen gases. • 

When sulphocyanate of ammonia is distilled, it is decom- 
posed, affording ammonia, bisulphuret of carbon, and a white 
powder called melam, which will be afterwards described. 
A mixture of muriate of ammonia and sulphocyanate of pot 
ash affords the same products. 

The soluble sulphocyanates are characterized by striking a 
deep blood-red color with persalts of iron. The color is so 






SULPHOC VACATES. 441 

intense that these substances are most delicate tests for each 
other. The seleniocyanates, in which selenium replaces oxy- 
gen, are similar to the sulphocyanates. 

Results of the complication of the Cyanids. 

881. The cyanates exhibit a strong tendency to form poly 
meric bodies by the union of three or more molecules of the 
original compound ; and thus give origin to a new class of 
substances, which are much more stable than the preceding. 
When hydrocyanic acid and chlorine are mixed and exposed 
to the sun-light, a white crystalline matter is deposited which 
contains the same proportion of the elements as the gaseous 
compound described under hydrocyanic acid ; but its vapor 
has three times the density of this, and its composition is 
represented by C 6 C1 3 N 3 . When its alcoholic solution is mixed 
with one of ammonia, it takes up the elements of six equiva- 
lents of water, and is converted into hydrochloric and cyanuric 
acids, which combine with the ammonia, C 6 Cl 3 N 3 -f 6HO= 
C 6 H 3 N 3 6 + 3HC1. 

882. Cyanuric Acid. — This acid is polymeric of the 
cyanic, three equivalents of which unite to form one of the 
cyanuric, 3C 2 HN0 2 =C 6 H 3 N 3 6 . When a solution of cyanate 
of potash is mixed with a quantity of acetic acid sufficient 
to decompose two-thirds of it, a cyanurate of potash is 
deposited. Cyanuric acid is readily formed by the decompo- 
sition of urea, three equivalents of which, 3C 2 H 4 N 2 2 = 
C 6 H 3 N 3 6 +3NH 3 . Pure urea is maintained in a state of 
fusion until the evolution of ammonia ceases, and it is 
changed into a grayish white mass. This is dissolved in 
concentrated sulphuric acid, and nitric acid is added drop by 
drop until the solution is decolorized ; it is then mixed with 
its bulk of water, and on cooling deposits the cyanuric acid 
in crystals. It is inodorous, and has a feebly acid taste ; it 
may be dissolved in strong acids without change, but when 
long boiled with them is decomposed, like the cyanic, into 
carbonic acid and ammonia. When heated, it divides into 
three equivalents of cyanic acid, which is thus obtained pure. 
The cyanuric acid is tribasic, and forms three classes of 
salts, in which one, two, and three equivalents of its hydrogen 
are replaced by a metal. 

883. The substance mentioned as a product of the distilla- 
tion of sulphocyanate of ammonia, under the name of melam, 
(880,) is a mixture of mellon with another compound, to 



442 ORGANIC CHEMISTRY. 

which the name of melamine is given. This substance is 
an amide of cyanuric acid, and corresponds to the cyanurate, 
with three equivalents of ammonia, which has lost the elements 
of six equivalents of water, C 6 H 3 N 3 6 ,3NH 3 — 6HO=C 6 H6N 6 . 
It is obtained by dissolving the melam in a dilute solution of 
potash, and crystallizes, on cooling, in fine rhombic octahe- 
drons. Melamine partakes of the characters of an organic 
base, and combines with acids, forming crystalline com- 
pounds. When boiled with acids or alkalies, it takes the 
elements of two equivalents of water, with the evolution of 
one of ammonia, and forms ammeline^ C 6 H 5 N 5 2 , which is 
the amide of the bi-ammoniacal cyanurate ; the farther 
action of acids yields ammelide, C 6 H 4 N 4 4 ; the amide of 
the cyanurate, with one equivalent of ammonia. All of 
these bodies are decomposed by long continued ebullition with 
strong acids. They reassume the elements of water, and 
form cyanuric acid and ammonia. 

COMPLEX CYANIDS. 

884. Several equivalents of the metallic cyanids often 
combine together to form compounds in which a portion of 
ihf metals is so united as to be no longer recognised by the 
ordinary tests. The cyanid of potassium unites with the 
cyanid of iron, and the product has none of the poisonous 
properties of the simple cyanid, nor is the iron precipitated, 
as in the ordinary compounds of that metal, by potash and 
alkaline sulphurets. These complex salts may be considered 
as derived from the union of six equivalents of the simple 
cyanids. A portion of the metal is replaced by hydrogen 
and other metals. 

885. Ferrocyanids. — A solution of cyanid of potassium 
dissolves metallic iron with the evolution of hydrogen gas, 
and the formation of a cyanid : oxyd of iron effects a similar 
decomposition, C 2 KN'+ FeO = KO + C 2 FeN. Two equiva- 
lents of the resulting cyanid of iron unite with four of cyanid 
of potassium to form the ferrocyanid of potassium, 2C 2 FeN + 
4C 2 KNCi 2 (Fe2K 4 )N 6 . This is the salt which has been already 
mentioned under the name of the yellow prussiate of potash. 
It is prepared on a great scale for the uses of the arts. For 
this purpose • animal matters, such as dried blood, horns, 
leather, and other azotized substances, are calcined in close 
vessels with carbonate of potash. In place of the animal 



COMPLEX CYANIDS. 443 

matters themselves, the coal produced by their calcination in 
close vessels, (animal charcoal,) which contains nitrogen, 
may be employed. The alkaline mass, which consists of 
impure cyanid of potassium, and an excess of the alkaline 
carbonate, is digested with water, and protosulphate of iron 
is added until the precipitate of oxyd of iron, at first formed, 
no longer dissolves ; the liquid is then filtered and evaporated, 
when it deposits the ferrocyanid. This salt forms large 
tabular crystals, which belong to the trimetric system, and 
have a fine lemon-yellow color; they contain six equivalents 
of water, which are expelled at 212°. It is very soluble in 
water, but insoluble in alcohol ; its taste is slightly saline, 
and it is not at all poisonous, but in large doses is purgative. 
Tt is employed in the arts for the manufacture of Prussian 
blue, and in dyeing. When fused with carbonate of potash 
it is decomposed, and affords a mixture of cyanate and cyanid 
of potassium with metallic iron.* Sulphuric acid decom- 
poses it in part, with the evolution of hydrocyanic acid.f 

* Upon this reaction M. Liebig has founded a very easy process 
for preparing cyanid of potassium. Eight parts of the carefully- 
dried ferrocyanid and three parts of pure carbonate of potash are 
intimately mixed and fused in a crucible (one of iron is to be pre- 
ferred) at a bright red heat until the evolution of gas ceases, and the 
mass is in quiet fusion. It is then removed from the fire, and after 
standing a short time to allow the suspended iron to subside, is 
poured upon a clean heated surface of stone or porcelain. The 
cooled mass, which should be perfectly white, is broken up and pre- 
served in well closed bottles. The cyanid thus prepared contains 
about one-fifth of cyanate, but is well suited for all the purposes of 
the arts, and of chemical analysis. 

t A dilute acid is readily prepared by distilling a mixture of two 
parts of ferrocyanid of potassium, one of sulphuric acid, and two 
of water, and collecting the product in a receiver containing two 
parts of water, until the liquid amounts to four parts. This acid, 
from the presence of a trace of sulphuric ' acid, is not liable to 
decomposition ; it contains 15 or 20 per cent, of pure acid. To 
determine the amount of real acid present, a weighed quantity of 
the distilled acid is added to a solution of nitrate of silver, which 
should be in excess ; the precipitate of cyanid of silver is collected 
on a filter, dried at 212°, and weighed. Its weight divided by 5 
gives the amount of real acid in the specimen. Let us suppose that 
70 grains of the acid yield SO of cyanid of silver, equal to 16 of real 
acid, 70 : 16 : : 100 : x, which equals 22-85 ; it then contains 22-85 
per cent, of real acid. But if it is required to reduce it to any 
standard, as one of 3 per cent., which is the ordinary medicinal acid, 
then as this will consist of 97 of water and 3 of real acid, 3 : 97 : : 
16 : x, and x = 517*3 grains of water, which must be added to 16 of 



444 ORGANIC CHEMISTRY. 

886. When a concentrated solution of the ferrocyanid is 
anixed with strong hydrochloric acid, and agitated with 
ether, a white crystalline substance separates, which must be 
washed with ether, and dried in vacuo. This is ferrocyanic 
acid corresponding to the previous compound in which the 
potassium is replaced by hydrogen ; its formula is C 12 (Fe 2 H 4 ) 
N 6 . It is acid and astringent to the taste, and is readily 
decomposed by exposure to the air. When a solution of 
ferrocyanid of potassium is mixed with the salts of lime, 
baryta, and zinc, it forms white precipitates which have the 
composition C 12 (Fe2KCa 3 )N 6 , &c. With salts of copper it 
affords an analogous compound of a deep reddish brown 
color ; this is a very delicate test for that metal. The pre- 
cipitate with protosaits of iron has similar composition ; it is 
of a greenish white, but turns blue by exposure to the air. 
With persalts of iron a deep blue precipitate is formed, which 
is the well known pigment, Prussian blue. It contains C 12 
(Fe2Fe 2 | )N 6 . In treating of the sesqui-salts, (676,) it was 
shown that in them two equivalents of iron replaced three 
of hydrogen, and consequently Fe* is substituted for H. If 
we represent Fei by Fe#, the composition of Prussian blue 
will be Ci 2 (Fe2Fe?)N. To obtain the ferrocyanid of iron 
in a state of purity, it is necessary that the persalt of 
iron should be in excess ; otherwise the precipitate contains 
potassium, and is C^FejKFe^N. Pure Prussian blue 
forms a light porous mass of a deep violet blue, with a 
coppery red reflection. It is quite insoluble in water and 
dilute acids ; but when recently precipitated is very soluble 
in oxalic acid and tartrate of ammonia, forming deep blue 
solutions, which are used as writing inks. When boiled 
with a solution of potash, peroxyd of iron separates, and 
ferrocyanid of potassium remains in solution. 

887. Ferridcyanid of Potassium ; Red Prussia te of Pot- 
ash. — This salt is obtained when chlorine is passed through a 
dilute solution of the ferrocyanid of potassium, until the 
solution no longer precipitates the persalt of iron. It is then 
concentrated by evaporation, and on cooling deposits crystals 
of the new salt, which are purified by a second crystalliza- 

anhydrous acid to reduce it to the standard. But as 70 grains of 
this acid contain already 54 of water, it is obvious that we have to 
add 517-3— 54=463-3 grains of water to 70 grains of acid to reduce 
it to the required standard. 



COMPLEX CYANIDS. 44-5 

tion. The mother liquor contains chlorid of potassium, 
C^Fe^Ne + C^KCl + C^FeJQNe. If we consider that 
Fe 2 =Fef, it will be seen that the salt is referable to the same 
type as the yellow prussiate, being (^(Fe^K^Ng. This beau- 
tiful salt crystallizes in large prisms of a deep crimson red ; 
when reduced to powder it is yellow ; it is readily soluble in 
water, anhydrous, and unalterable in the air. The solution 
of this salt does not affect the persalts of iron, but throws 
down from the solution of the protosalts a fine blue precipi- 
tate, which is C 12 (Fe^Fe 3 )N 6 . Its hue is finer than that of 
the ferrocyanid of iron, and it is known in the arts as Turn- 
bull's blue. 

888. The Ferridcyanic Acid is obtained by decomposing 
the ferridcyanid of lead by dilute sulphuric acid. Its formula 
is Ci 2 (Fe^H 3 )N 6 . Chromium and cobalt form compounds 
precisely similar in their composition to the ferridcyanid. 

889. Platino-Cyanids. — The platino-cyanid of potas- 
sium, Ci 2 (Pt 3 H 3 )N 6 , is obtained by heating to low redness a 
mixture of equal parts of dried ferrocyanid of potassium and 
spongy platinum ; the mass is digested with water and con- 
centrated by evaporation, when the salt is deposited in long 
transparent, rhomboidal prisms, which are yellow by re- 
flected, and blue by transmitted light. The platino-cyanic 
acid, C 12 (Pt 3 H 3 )N, is obtained by decomposing the insoluble 
platino-cyanid of mercury by sulphureted hydrogen ; it crys- 
tallizes in fine golden-yellow needles with a coppery red 
reflection. 

890. The other polymeric cyanids have been little studied. 
The cyanid of silver is readily soluble in cyanid of potas- 
sium, and the solution affords tabular crystals of a double 
salt which appears to correspond to the platino-cyanid, being 
C 12 (Ag 3 K 3 )N 6 . The silver in this compound is not preci- 
pitated by alkaline chlorids, but strong acids decompose it 
with the evolution of hydrocyanic acid and the precipitation 
of cyanid of silver. With acetate of lead it gives a preci- 
pitate in which lead replaces the potassium. The two cyanids 
of gold are soluble in cyanid of potassium, and probably 
form analogous compounds. 

891. These solutions are much employed in electro-gilding ; 
the precious metals being always deposited from solutions of 
their double cyanids. These are generally prepared by 
adding the oxyds to a solution of cyanid of potassium ; they 

38 



4-46 ORGANIC CHEMISTRY. 

are readily dissolved, and the double salts formed with the 
separation of potash.* 

FULMINATES. 

892. The mutual action of nitric acid, alcohol, and nitrate 
of silver or mercury, gives rise, to salts which are distinguished 
by exploding violently by heat or percussion, and have hence 
been described under the name of fulminates. 

The Fulminate of Mercury (C 4 Hg 2 N 2 4 ) is prepared by 
the following process : One ounce of mercury is dissolved, by 
a gentle heat, in an ounce and a half, by measure, of nitric 
acid, specific gravity 1*4, and the solution poured into ten 
measured ounces of alcohol, specific gravity -830. A violent 
action takes place, after a few minutes, with the evolution 
of copious white fumes ; after this is over the fulminate 
is found in white crystalline grains ; it is to be carefully 
washed with cold water, and dried by a gentle heat. 
*It is slightly soluble in boiling water, and crystallizes, on 
cooling, in feathery crystals. It explodes violently by a heat 
of 390°, by the contact of concentrated sulphuric and nitric 
acids, or by percussion, and is employed in the preparation 
of the percussion caps for fire-arms. 

893. The Fulminate of Silver (C 4 Ag 2 N 2 4 ) is prepared 
by a similar process. It is much more dangerous than the 
last ; the slightest friction between two hard surfaces, even 
under water, will cause it to explode with fearful violence. 
It is very poisonous. 

The true nature of these compounds is not known ; they 
have been regarded as the salts of a bibasic acid, C 4 H 2 N 2 4 , 
which is polymeric of cyanic acid ; but this acid is unknown. 
One equivalent of the metal is combined, as in the complex 
cyanids, in such a manner that it cannot be separated by the 
ordinary reagents ; the other equivalent is capable of being 
replaced. When the silver salt is dissolved in acid, one-half 
of its silver separates, and an acid salt crystallizes on 
cooling, which is C 4 AgHN 2 4 ; potash or baryta, in the same 
way, precipitate one equivalent of silver, and form salts of 
the formula C 4 AgKN 2 4 . M. Gerhardt regards them as 
nitric species of a genus which is the homologue of the 

* For this classification of the cyanids, as well as for many other 
important aids, this portion of the work is indebted to M. Gerhardt's 
excellent Precis de Chimie organique. 



ALCARSINE, AND THE BODIES DERIVED FROM IT. 447 

cyanids, and will be C 4 H 3 N. The nitric species, in which 
the residue of nitric acid (675) NH0 6 — 2 replaces H 2 , will 
be C 4 H(NH0 4 )N=C 4 H. 2 N 2 4 . The reasons for this are the 
resemblance of the fulminates to the complex cyanids, and 
the results of their decomposition by sulphureted hydrogen, 
which is analogous to that of other nitric compounds. 

ALCARSINE, AND THE BODIES DERIVED FROM IT. 

894. When a mixture of equal parts of arsenious acid and 
acetate of potash is distilled at a low red heat, there is 
obtained, among other products, a volatile liquid to which 
the name of alcarsine is given. When purified it is a 
colorless liquid, slightly soluble in water, and of specific 
gravity 1*462 ; it boils at 300°, and distils unchanged. 
Its odor is very disagreeable, resembling arseniureted 
hydrogen ; applied to the skin it is corrosive, and taken in- 
ternally it is an energetic poison. Exposed to the air it 
takes fire and burns with a white flame, evolving vapors of 
arsenious acid. The formula of alcarsine is C s H 12 As 2 2 ; 
four equivalents of acetic and two of arsenious acid contain 
the elements of eight equivalents of carbonic acid, four of 
water, and one of alcarsine ; carbonate of potash remains. 
Alcarsine combines directly with acids, forming crystalline 
compounds ; it is a true alkaloid, in which arsenic replaces 
nitrogen. The oxygen in this substance may be replaced 
by sulphur and selenium, forming compounds which resemble 
the normal alcarsine. 

895. When alcarsine is distilled with concentrated hydro- 
chloric acid or chlorid of mercury, a colorless liquid is 
obtained, which is called chlorarsine. One equivalent of 
alcarsine and two of hydrochloric acid yield two of water 
and two of chlorarsine, C 8 H 12 2 As 2 + 2HCl=2HO + 2C 4 H 5 
AsCl. It has a most disgusting odor, and its vapor is 
spontaneously inflammable. Similar compounds are obtained 
with hydrobromic and hydriodic acids. Chlorarsine is 
decomposed by salts of silver, which precipitate all its 
chlorine ; this element appears to exist in it as hydrochloric 
acid. These compounds may be regarded as the salts of an 
alkaloid, arsine, which is C 4 H 5 As, and the hydrochlorate 
will be C 4 H 5 As,HCl. The arsine has not yet been isolated, 
but the compounds above described are precisely similar to 
the salts of the alkaloids. 



448 ORGANIC CHEMISTRY. 

896. When chlorarsine is digested with zinc or iron, at a 
temperature of 212°, a metallic chlorid is formed without 
any evolution of gas, and a liquid remains, to which M. 
Bunsen, its discoverer, has given the name of kakodyle* 
He assigns to it the formula, C 4 H 6 As, and regards it as the 
radical of the previous compounds, and as combining directly 
with oxygen and chlorine like a metal ; but its real formula 
is C 8 H 12 As 2 , and it cannot consequently exist in chlorarsine, 
whose equivalent, as deduced from its compounds and the 
specific gravity of its vapor, is represented by C 4 H 6 As,HCl. 
Its relations to these compounds is analogous to that which 
exists between cyanogen and the cyanids. Kakodyle is a 
colorless liquid, of a most disagreeable odor, and is fearfully 
poisonous ; it fumes and takes fire on exposure to the air, 
but if covered by water, is slowly oxydized and yields alcar- 
sine. 

897. When kakodyle and alcarsine are gradually oxy- 
dized at a low temperature, a crystalline compound is 
obtained, which is called alcargene. It is best obtained by 
bringing alcarsine in contact with oxyd of mercury under 
water ; metallic mercury separates, and pure alcargene remains 
in solution. Its composition is C 4 H 5 As0 4 ; one equivalent of 
alcarsine and eight of oxygen yield two of water, and two 
of the new compound, C 8 H ia As 2 2 + 80=2HO + 2C 4 H 5 As0 4 . 
This body forms large transparent rhombic prisms, readily 
soluble in water, and less so in alcohol. It is inodorous, has 
a feeble taste, and is not at all poisonous, even in large doses. 
It may be boiled with nitric acid without change, but deoxy- 
dizing agents convert it into alcarsine. Alcargene combines 
with acids and salts, like an alkaloid, while, at the same time, 
it acts as aa acid, and decomposes the alkaline carbonates, 
forming monobasic salts. By the action of dry sulphureted 
hydrogen, a compound is obtained, in which the oxygen is 
replaced by sulphur. It forms large colorless crystals of an 
alliaceous odor, having the formula C 4 H 5 AsS 4 . 

URIC ACID, AND THE PRODUCTS OF ITS DECOMPOSITION. 

898. This substance is found in the urinary secretion of 
nearly all animals ; the solid urine of serpents, birds, and 

* Fjrom the Greek Jcakos, evil, and hule, principle, in allusion to its 
noxious properties. 



URIC ACID, AND THE PRODUCTS OF ITS DECOMPOSITION. 449 

insects, is almost entirely urate of ammonia. To prepare it, 
the urine of the boa constrictor, or other serpents, is boiled 
with a solution of caustic potash, until the evolution of am- 
monia ceases. A current of carbonic acid gas is then passed 
through the liquid, which precipitates urate of potash, while 
the impurities are held in solution. This precipitate is washed 
with cold water, in which it is sparingly soluble, and dis- 
solved in a dilute solution of potash ; from this solution, 
hydrochloric acid precipitates uric acid in a gelatinous mass, 
which by a gentle heat changes into a crystalline precipitate. 
It is a white crystalline powder, which is almost insoluble in 
water; it is bibasic, and its formula is Ci H 4 N 4 O 6 . The 
urates are very sparingly soluble salts. 

899. By the action of oxydizing agents, uric acid yields 
many interesting products. Boiled with peroxyd of lead, 
carbonic acid gas is evolved, and the liquid contains a crys- 
talline compound called allantoine, which exists in the am- 
niotic fluid of the cow. Its composition is C 8 H 6 N 4 6 . The 
reaction is thus expressed : C, O 4 N 4 O 6 + 2HO + 2Pb0 2 = 
2C0 2 + C 8 H 6 N 4 6 + 2PbO. The farther action of peroxyd 
of lead converts allantoine into urea and oxalate of lead, 
C 8 H 6 N 4 6 + 2HO + 2Pb0 2 equals two equivalents of urea 
2C 2 H 4 N 2 2 , and one of oxalate of lead, C 4 Pb 2 8 . 

When uric acid is gradually added to four times its weight 
of nitric acid, specific gravity 1-425, it dissolves with the evo- 
lution of carbonic acid and nitrous vapors, and, on cooling, 
deposits alloxan, which, by a second crystallization, is obtained 
in large colorless prisms very soluble in water ; the mother 
liquor contains ammonia. Its formula is C 8 H 4 N 2 O I0 . One 
equivalent of uric acid with six of water, and two equivalents 
of oxygen from the nitric acid, yield two equivalents of car- 
bonic acid, two of ammonia, and one of alloxan. C ]0 H 4 N 4 O 6 -f- 
6HO + 20 *= 9C0 2 + 2NH 3 -f C 8 H 4 N 2 O 10 . If the nitric acid is 
either more concentrated or more dilute, or if heat is applied, 
the nitrous acid formed reacts upon the ammonia, and from 
their mutual decomposition nitrogen gas is evolved. The 
farther oxydation of alloxan transforms it into carbonic gas, 
oxalic acid, and urea, and hence these latter substances are 
found as secondary products of the action of nitric upon uric 
acid. 

900. By the action of deoxydizing agents alloxan is con- 
verted into alloxantine ; if a solution of it is mixed with 
hydrochloric acid and placed in contact with a slip of zinc, 

38* 



450 ORGANIC CHEMISTRY. 

it deposits crystals of alloxantine; the same change is 
effected by the action of sulphurated hydrogen gas. Allox- 
antine is also obtained when an excess of uric acid is added 
to dilute boiling nitric acid ; its formula is C 16 H 10 N 4 O 20 , and it 
is derived from the elements of two equivalents of alloxan by 
the addition of two of hydrogen, 2C 8 H 4 N 2 O 10 +2H=C 16 H, 
N4O20. Alloxantine bears the same relation to alloxan as 
indigogene does to indigo. It forms colorless prisms very 
sparingly soluble in cold water; when boiled with dilute 
nitric acid it is converted into alloxan. When its solution is 
mixed with a solution of sal ammoniac, crystals of uramile 
(C 8 H 5 N 3 6 ) are deposited, and the liquid contains alloxan and 
free hydrochloric acid, C ]6 H 10 N 4 O ?0 + HCl,NH3=C 8 H 5 N 3 O 6 + 
HCl + C 8 H 4 N 2 O 10 +4HO. Uramile is the amide of dialuric 
acid, (C 8 H 4 N 2 8 ,) and when boiled with alkalies or acids 
takes up the elements of water and is converted into am- 
monia and this acid, which is also obtained by the prolonged 
action of sulphureted hydrogen upon a solution of alloxantine. 

901. When carbonate of ammonia is added drop by drop 
to a solution of alloxan maintained nearly at the boiling- 
point, carbonic acid is disengaged and the liquor becomes 
purple ; the addition is continued until the liquid has a feeble 
odor of ammonia, and it is then set aside to cool, when it 
deposits crystals of murexide. This beautiful substance 
forms square prisms, which have a magnificent golden-green 
color like the wing-cases of the golden beetle; by trans- 
mitted light they are garnet-red. Murexide is sparingly 
soluble in water ; its formula is C, 6 H 8 N 8 8 , and it is formed 
from two equivalents of alloxan and four of ammonia by the 
separation of twelve of water, 2C 8 H 4 N 2 O 10 + 4NH 3 =C, 6 H 8 N 3 
O g -f 12HO. Murexide is produced in several other reactions ; 
when a solution of uramide, with a little ammonia, is boiled 
with oxyd of silver, crystals of it are deposited while the 
metal is reduced. The same solution gradually absorbs 
oxygen from the air, and undergoes the same change ; two 
equivalents of uramile, with two of ammonia and four of 
oxvgen, yield one of murexide and eight of water, 2C 8 H 5 N 3 
6 + 2NH 3 +0 4 =C 16 H 8 N 8 8 +8HO. The solution of uric 
acid in strong nitric acid may be employed in place of alloxan 
for the preparation of this substance. 

902. When uric acid or alloxan is boiled for some time 
with an excess of strong nitric acid, it evolves carbonic acid, 
and deposits on evaporation and cooling crystals of para 



HIPPURIC^ ACID. 4-51 

banic acid, C 6 H 2 N 2 6 . This substance is very soluble, and 
has a well marked acid reaction ; when its solution is neu- 
tralized by ammonia and boiled, it combines with the 
elements of two equivalents of water, and is converted into 
oxalurate of ammonia. The oxaluric acid is C 6 H 4 N 2 8 ; 
when its solution is boiled it takes the elements of two 
equivalents of water, and is resolved into oxalic acid and 
urea, C 6 H 4 N 2 8 + 2HO = C 4 H 2 O s + C 2 H 4 N 2 2 . 

Uric acid yields many other products of interest, which 
are described in the larger works ; the study of these 
reactions is very instructive, as it shows us the effects of 
different reagents, and the laws which regulate the trans- 
formations of substances. 

HIPPURIC ACID. 

903. This substance exists in human urine, or in still 
larger quantities in that of cows and horses. From the 
latter it may be prepared by mixing the fresh urine with 
milk of lime until it acquires an alkaline reaction. The 
precipitate formed is allowed to subside, and the clean liquid 
rapidly evaporated to about one-tenth. It is then mixed with 
a slight excess of hydrochloric acid, which on cooling sepa- 
rates impure hippuric acid. This is purified by solution in hot 
water, and digesting with a little animal charcoal ; the 
filtered solution deposits pure hippuric acid on cooling. It 
forms large white prisms, and is readily soluble in hot water, 
but requiring 400 parts of cold water for solution.* Its 
formula is C 18 H 9 N0 6 . When hippuric acid is boiled with 
peroxyd of lead it evolves carbonic acid, and the solution 
contains benzamide, C 18 H 9 N0 6 + 6 = C 14 H 7 N0 2 -f 4C0 2 + 
2HO. If a solution of hippuric is boiled for half an hour 
with a strong acid, as the hydrochloric, it deposits on cooling 
a large quantity of benzoic acid, and the liquid by evaporation 
affords crystals, which are a compound of hydrochloric acid, 



* A curious instance of the formation of hippuric acid is observed 
when benzoic acid is taken into the stomach ; an adult can swallow 
half an ounce of it without any unpleasant effects, and in the course 
of eight or ten hours the excreted urine will contain an amount of 
hippuric acid equivalent to that of the benzoic acid taken, while the 
normal urine contains but a very small portion of it. It is hence 
inferred that the hippuric is formed from the benzoic acid by 
the action of the organism, but no process is known by which it can 
be produced artificially. 



452 ORGANIC .CHEMISTRY. 

with a peculiar sweet substance which was originally 
obtained by the decomposition of gelatine, and hence named 
glycocoll,* or sugar of gelatine, C 18 H 9 N0 6 -f 2HO=C 14 H60 4 
+ C 4 H 5 N0 4 . 

904. Glycocoll has a taste resembling that of grape sugar ; 
it is nearly insoluble in alcohol, but soluble in four or five 
parts of water, and crystallizes readily from its solutions. 
It combines directly with the acids to form beautifully crystal- 
lized compounds, in which it appears to act the part of an 
organic base. At the same time it dissolves metallic oxyds, 
and forms compounds, in which an equivalent of its hydrogen 
is replaced by a metal. 

Glycocoll is closely related to alcargene, which may be 
regarded as glycocoll in which arsenic takes the place of 
nitrogen ; these two substances also resemble each other in 
performing the double function of bases and acids, and in 
their general physical characters. 

NUTRITIVE SUBSTANCES CONTAINING NITROGEN. 

905. All vegetables afford, in addition to lignine, starch, 
sugar, and the other bodies before described, a peculiar class 
of compounds which contain nitrogen and a small quantity 
of sulphur. These substances are tasteless, often insoluble 
in water, and are highly nutritious. They occur to a still 
greater extent in animals, of which they constitute the mus- 
cular fibre, and are dissolved in the fluids of the body. 
These substances are very analogous in their composition 
and chemical characters. 

906. Vegetable albumen is found in the juices of many 
plants. It closely resembles animal albumen, and like it is 
coagulated by heat. When a paste of wheat flour is washed 
with water, a large quantity of starch separates, and a very 
tenacious substance remains, which is known as gluten, 
and is principally vegetable fibrine. It forms a gray trans- 
lucent mass which is soluble in acetic acid. Legumine, or 
vegetable caseine, is found in the seeds of beans and peas. 
When the seeds are bruised with water, the legumine dis- 
solves ; acetic acid coagulates the solution, and precipitates 
it in a form resembling the curd of milk. 

907. These substances are very prone to decomposition, 

* From the Greek glukus, sweet, and kolla, glue. 



NUTRITIVE SUBSTANCES CONTAINING NITROGEN. 453 

and when exposed to air and moisture, soon undergo putre- 
faction. The remarkable power which they possess to in- 
duce change in other bpdies has been frequently noticed. The 
conversion of sugar into lactic and butyric acids, is due to the 
action of decomposing caseine, (772,) and synaptase, (856,) 
which is an analogous compound, probably owes its singular 
power of decomposing amygdaline and emulsine to a similar 
condition. Diastase (780,) is a modified form of gluten. 
Yeast, (770,) which is a deposit from beer and other fermenting 
liquids, is similar to these, and identical with the substance men- 
tioned as producing the vinous fermentation. The process of 
bread-making illustrates the action of this substance. The 
essential ingredients in flour are vegetable fibrine, starch, and 
sugar. The flour is made into a paste with water, yeast is 
added, and the mixture is put in a warm place. The yeast 
induces the vinous fermentation in the sugar, forming alcohol 
and carbonic acid gas, which, from the viscid nature of the 
paste, inflates it, and gives to it its peculiar lightness and 
porosity. The power of yeast and similar bodies is com- 
pletely destroyed by boiling water, strong alcohol, essential 
oils, various metallic salts, and many other substances, all of 
which are known to act as antiseptics. 

908. Animal Albumen. — This substance is found abun- 
dantly in the white of eggs and the serum of the blood. Al- 
bumen is soluble in water, especially with the aid of an 
alkali, but is readily precipitated from its solutions by acids. 
When exposed to a temperature of about 150°, it is changed 
into a white mass which is no longer soluble. 

Animal Fibrine. — This substance is dissolved in the 
chyle and blood, and constitutes the muscular parts of animals. 
It is easily obtained by stirring freshly drawn bullock's 
blood ; the fibrine adheres to the stick and may afterwards 
be washed with water. It is a white fibrous mass, which 
when dry is horny and translucent. Fibrine is readily solu- 
ble by a gentle heat in solutions of sal ammoniac, nitre, and 
several other salts. When thus dissolved, it has the proper- 
ties of soluble albumen and is coagulated by heat. Both 
fibrine and coagulated albumen are soluble in water, contain- 
ing 2oVo" tn P art °f hydrochloric acid. 

909. Caseine. — This substance constitutes the curd of 
milk. When pure it is quite insoluble in water ; but in milk 
it is rendered soluble by combination with a little alkali. Its 
solution is immediately coagulated by dilute acids, which 



454 ORGANIC CHEMISTRY. 

combine with the precipitated caseine. The spontaneous 
coagulation of milk is due to the formation of lactic acid 
from the sugar of milk, by the agency of a portion of the 
caseine in a state of insipient decomposition, (772.) This 
change goes on until the whole of the sugar is converted into 
lactic acid. In the manufacture of cheese, the process is 
facilitated by the addition of a little rennet. This substance 
is prepared by digesting the lining membrane of a calf's 
stomach in water, and appears to act like caseine by impart- 
ing to the milk its peculiar condition. 

910. Proteine. — When any one of these bodies is dis- 
solved in a dilute solution of potash by a gentle heat, acetic 
acid precipitates from the liquid a white pulverulent substance, 
which Mulder, its discoverer, has named proteine.* The 
composition of this body is the same, from whatever source 
it is obtained, and leads to the formula C 40 H3oN 5 12 . The 
substances from which it is derived always contain phosphate 
of lime, and frequently salts of soda. Beside this, there is 
invariably present a small portion of sulphur, and in albumen 
and fibrine, traces of phosphorus. The quantity of sulphur 
is small, being on an average about 2iro" tn P ar * 5 i* * s sepa- 
rated in the form of sulphuret of potassium when the sub- 
stance is dissolved in potash, and can be detected by a salt of 
lead, which affords with the solution a black precipitate of 
sulphuret of lead. The proportions of oxygen, hydrogen, 
nitrogen, and carbon, in these bodies are the same as those in 
proteine. 

911. We may conceive proteine to be allied to fibrine, 
albumen, &c, in the same manner as dextrine is to starch 
and cellulose. The different condition of these several sub- 
stances may be regarded as the result of organization, for 
we have seen that fibrine may be readily converted into 
albumen without any change of composition. The sulphur 
in these compounds is probably due to the presence of a sul- 
phureted body not yet separated, which is decomposed by the 
potash. As its quantity is very small and the proportions of 
its organic elements quite similar to those of proteine, we 
observe no difference between the analyses of proteine and 
the organic tissues. 

912. Proteine and all the bodies of this class are soluble 



* From the Greek, proteuo, I take the pre-eminence, in allusion to 
the large class of substances of which it is supposed to be the basis. 



THE BLOOD. 455 

in strong hot hydrochloric acid, and yield a purple solution, 
which., by exposure to the air, absorbs oxygen and becomes 
black. It then contains sal ammoniac and a substance identical 
with the humic acid noticed before (785) as a result of the 
decay of woody fibre ; its composition may be expressed by 
the formula C 40 H 12 O 12 . The elements of one equivalent of 
proteine and three of oxygen yield humic acid with five equi- 
valents of ammonia, which unite with the hydrochloric acid 
and three of water, C i0 U 30 N s O 12 +SO=C 4Q U l2 O 12 -i-5NU 3 + 
3HO. 

913. Gelatine. — This substance is obtained from many 
animal tissues, as the skin, cellular membranes, tendons, and 
ligaments, and also from the bones, which contain about forty 
per cent, of soluble matters. It is extracted from these sub- 
stances by boiling with water, and the solution on cooling 
becomes a firm jelly ; this property is very characteristic of 
gelatine. It is found nearly pure in isinglass or fish glue. 
This substance does not exist in the tissues in a soluble form, 
but in a condition which is probably related to the soluble 
gelatine as starch is to dextrine, (779.) It is in fact a pro- 
duct of the action of boiling water upon the insoluble gelatine. 
Its solution forms a very insoluble precipitate with an infusion 
of nut-galls, or a solution of tannic acid. When the skin of 
animals is steeped in an infusion of oak bark or of any other 
vegetable containing tannic acid, this insoluble compound is 
formed and constitutes leather. The formula of gelatine is 
Ci 3 H 10 N 2 O 5 . The substance of cartilage has been named 
chondrine ; it resembles gelatine in its properties, but differs 
a little in composition ; both of these bodies, like the proteine 
compounds, contain traces of sulphur. 

914. If one part of gelatine is mixed with two of concen- 
trated sulphuric acid, it dissolves in a few hours, and forms 
a viscid liquid ; this is diluted with nine parts of water, and 
boiled for six or eight hours ; the acid is then neutralized by 
chalk, and the clear liquid evaporated to a syrup, which 
gradually deposits transparent crystals of glycocoll or sugar 
of gelatine, (903.) 

THE BLOOD. 

915. This substance, when recently taken from the body, 
is a homogeneous slightly viscid liquid, but soon forms a 
tremulous jelly, which by standing contracts into a hard 
coagulum, floating in a yellowish liquid called the serum. 



456 ORGANIC CHEMISTRY. 

This has a saline taste, and contains in solution alkaMne 
chlorids and phosphates, with a large portion of albumen. 
It has an alkaline reaction, which is due to the presence of 
the tribasic phosphate of soda. 

The coagulum of the blood has a dark-red color, and 
consists of a mass of fibrine mixed with the red globules, 
which constitute the coloring matter of the blood. If the 
fresh liquid is mixed with several volumes of a solution of 
sulphate of soda, the fibrine remains dissolved, (908,) and 
the globules collect at the bottom of the liquid as a sediment. 

916. The form and size of these globules vary in different 
animals ; in the blood of man they are thin discs from -3 oW 
to g-oVo" of an inch in diameter. They consist of a colorless 
sac, of a composition similar to fibrine, which encloses a 
soluble red matter. When placed in water, these corpuscles 
burst and form a red liquid containing albumen and the 
coloring principle, which is named hematine. This is 
readily soluble in alcohol containing a little acid or ammonia, 
by which it is separated from the albumen. The solution 
has a deep red color even when much diluted. Pure 
hematine contains about 6 per cent, of iron, which cannot be 
separated from it by dilute acids. Its composition may be 
expressed by the formula C^H^NaOgFe. If it is mixed with 
strong sulphuric acid, and water gradually added to the 
mixture, hydrogen gas is evolved, and the hematine separates 
as a dark-red mass, while the iron remains in solution. 
The hematine thus prepared is entirely free from iron ; but 
its composition is in other respects the same as before, being 
C^H^NaOg. This shows that the red color of the blood is 
not necessarily due to the compounds of iron, as has been 
supposed, and that the iron does not exist in the blood as an 
oxyd. 

917. The color of the arterial blood is scarlet, while that 
in the veins is a dark-red, and the solutions of hematine have 
the same tint. The venous blood acquires the bright scarlet 
tint while in the lungs, but loses it again in the capillary 
vessels. This change has been attributed to the absorption 
of oxygen by the coloring matter, but hematine undergoes 
no change of color by the action of the air. If we mix 
arterial blood with water, it immediately assumes a dark-red 
color, which is not altered by oxygen gas ; but a solution 
of any neutral salt will restore the scarlet tint, even in a 
vacuum. A little milk, or a mixture of chalk and water. 



THE GASTRIC JUICE. 457 

will immediately give a bright color to venous blood or a 
solution of hematine. This effect seems due to the light 
reflected from the white particles, and the saline liquids 
produce the same effect by coagulating the exterior of the 
globules and rendering them white. Mulder supposes that 
the action in the lungs consists in an oxydation of a portion 
of the fibrine of the blood, by which a white layer of oxyd 
of proteine is formed on the surface of the blood globules. 
This oxyd is taken up in the capillary vessels, and the 
globules reacquire their dark-red tint. This view must be 
considered as only an ingenious hypothesis, but it is certain 
that the difference of color is not due to any change in the 
hematine itself. 

918. In addition to the substances already mentioned, the 
blood contains globules of fatty matter. 1000 parts of blood 
afford 790 parts of water, 68 of albumen, and 10*9 parts 
of salts with a little fat, which are dissolved in the serum. 
The clot contains about 138*6 parts of albumen and fibrine, 
and 2' 97 parts of hematine, besides 2*4 parts of fatty sub- 
stances which contain phosphorus. The salts of the blood 
are principally alkaline chlorids and phosphates, with 
phosphate of lime. The proportions of the ingredients often 
differ from these, being varied by many circumstances. 

919. Chyle. — This fluid is taken up by the lacteals from 
the smaller intestines, as a white opake fluid. It contains 
a proteine compound in solution, and a great number of 
globules of fat to which its milky appearance is due, besides 
various salts, and a small portion of iron in a soluble form. 
When the chyle is first taken up by the lacteals, it contains but 
little fibrine, but a large portion of albumen. But the chyle 
from the thoracic duct coagulates like the blood into clots 
which contain fibrine, while the clear fluid that separates 
resembles the serum of the blood. Lymph, the fluid of the 
lymphatic vessels, differs from chyle principally in being 
more dilute, and in the absence of the fatty globules. 

THE GASTRIC JUICE. 

920. This fluid is secreted from the coats of the stomach 
by the stimulus of food. It is a slightly saline fluid with an 
acid reaction, and contains chlorid of sodium, traces of phos- 
phate of lime, a small quantity of dissolved animal matter, 
and a free acid. This, according to the experiments of 

39 



_ 



458 ORGANIC CHEMISTRY. 

Berard and Barreswil, is the lactic acid. The animal matter 
appears allied to the proteine compounds, and has been called 
pepsine ; but is probably not a distinct substance. The 
gastric juice has a remarkable solvent power ; muscular fibre, 
coagulated albumen, and various other substances are com- 
pletely dissolved by it. This property is not confined to the 
gastric juice while in the stomach ; when taken from the body 
it produces the same effect, if kept at the temperature of the 
system, (about 100° F.) If it is heated for a short time to 
200° F., this solvent power is completely destroyed ; the 
same effect is produced by neutralizing the free acid, but a 
small portion of any acid restores its activity. The solvent 
power of the gastric juice appears then to be due to the con- 
joined influence of the acid and animal matter. As the 
activity of this last is immediately destroyed by boiling water, 
alcohol, and some other antiseptic agents, it has been sup- 
posed to be a proteine body in a state of change, (907,) and 
the process of digestion is regarded as a kind of fermentation, 
induced by this substance with the aid of an acid. The 
change, however, appears scarcely analogous to any phe- 
nomena of this kind, and although this idea is probably the 
nearest approximation to the truth, the subject is still obscure. 

921 . The Saliva. — This fluid contains a peculiar animal 
matter which has been called ptyaline, with a considerable 
portion of saline matter ; this consists principally of chlorids 
of potassium and sodium, and the tribasic phosphate of soda, 
to which the alkaline reaction of the secretion is due. In 
addition to these are found small quantities of earthy phos- 
phates and a trace of sulphocyanid of potassium. The saliva 
appears, like the gastric juice, to have a solvent power on 
animal substances, and seems to prepare the food for the 
process of digestion. The pancreatic Jluid resembles the 
saliva in composition, but nothing definite is known as to its 
uses or properties. 

THE BILE. 

922. This fluid is a secretion of the liver, and is found in 
the gall-bladder. -.It is viscid, has a greenish-yellow color, 
and an alkaline reaction. Bile consists of the soda salt of a 
peculiar fatty acid, with a small portion of a crystalline fat 
called cholesterine, and a peculiar coloring matter. This 
acid is called the choleic, and b ; !e is a solution of choleate 
of soda. 



THE URINE. 459 

923. The bile and the other alkaline choleates have the 
characters of soaps, and the use of this liquid in removing 
oil stains depends upon this property. Its composition is, 
however, very different from that of the oily acids before 
described, as it contains nitrogen and sulphur. The formula 
which has been given is C^H^NO^, but as taurine, a product 
of its decomposition, has recently been found to contain a 
large amount of sulphur, this must be modified. 

The acid is slightly soluble in water, but readily in alcohol. 
When boiled with hydrochloric acid it is decomposed and 
affords a number of new substances. 

924. This fluid appears to perform an important part in 
digestion ; it mixes with the food in the duodenum, and ap- 
parently aids in the elaboration of the chyle. It is probable 
that, by its peculiar properties, it renders the fatty portions of 
the food soluble, and it is supposed by some that it has the 
power of converting starch and sugar into fat. This, how- 
ever, requires proof. Its presence appears essential to the 
assimilation of food ; if the duct which conveys the bile to 
the duodenum is divided, and an artificial outlet is provided 
for it,' the secretion is performed as before, yet the animal 
becomes emaciated and dies, apparently from imperfect nu- 
trition. Still, this fluid appears to be, to a great extent, an 
excretion of the system. 

THE URINE. 

925. This excrementitious fluid, which is separated from 
the blood by the action of the kidneys, is a medium for the 
removal of various saline and azotized matters which are 
unfitted for the purposes of life. The organic substances 
thus discharged, are urate of ammonia, urea, and hippuric 
acid. The urinary secretion of birds, reptiles, and insects, 
which is white and solid, is principally urate of ammonia. 
That of herbivorous animals contains urea and a large quan- 
tity of hippuric acid, which in the carnivora is entirely 
replaced by urea and a little uric acid. This is nearly the 
composition of that of man, subsisting on a mixed diet. 
The average proportion of urea in healthy human urine is 
about three per cent., but is varied by many causes. The 
amount of uric acid is about 16 1 0o of the urine ; in addition 
to these, it contains a small portion of hippuric acid and an 
organic coloring matter. The saline matters generally 



460 ORGANIC CHEMISTRY. 

amount to two or three per cent., and consist of chlorid of 
sodium, sulphates and phosphates of potassa and soda, with 
traces of ammoniacal salts, and phosphates of lime and mag- 
nesia. Fresh urine has an acid reaction, which is ascribes 
to the uric acid that is held in solution by the phosphate 
of soda. Pure urine undergoes no change by keeping, but 
when in contact with the mucus of the bladder it is rapidly 
decomposed, and the urea is converted into carbonate of 
ammonia, (874.) 

926. In diseased states of the system the composition 
of this fluid is sometimes altered, and the uric acid or 
earthy salts rendered less soluble or more abundantly 
secreted, are deposited in the bladder, forming stony concre- 
tions or calculi. They are most frequently uric acid or 
urates, and the phosphates of lime and magnesia ; oxalate 
of lime frequently occurs in this form, although oxalic acid 
does not exist in healthy urine. 

THE BRAIN AND NERVOUS MATTER. 

927. These substance have a close resemblance in their 
organization and chemical composition ; the white and gray 
portions of the brain differ principally in their structure. 
The brain contains about twenty per cent, of solid matter, 
the rest is water. About one-third of the solid substance 
resembles albumen ; the remainder is composed of several 
fatty substances, some of which are quite peculiar in their 
composition, from containing nitrogen and phosphorus ; the 
amount of this last element is about four per cent, of the 
solid matter. The cerebric acid is obtained in white crys- 
talline grains, and forms very insoluble salts. The oleo- 
phosphoric acid is a compound of phosphoric acid with an 
oil resembling oleine, and is decomposed into these, by long 
boiling with water. The cerebral substance contains besides 
these, the crystalline fat found in the bile, cholesterine, and 
some other substances which have not been thoroughly studied. 
The fatty matter of the blood, consists in part of cholesterine 
and a substance which contains nitrogen and phosphorus, 
and is analogous to cerebric acid. 

MILK. 

928. This secretion designed for the use of the young 
animal, contains all the substances necessary for its propei 



I. ONES. 461 

developement. The proportion of its ingredients is very- 
variable, but the following analysis of cows' milk may be 
taken as an average; 1000 parts contain water 873 ; butler 
30 ; caseine 48*2 ; milk sugar 43*9 ; phosphate of lime 2-3 ; 
chlorids of potassium and sodium 1-68, with small quantities 
of phosphates of iron and magnesia, besides soda in combi- 
nation with caseine. These substances have been already 
described under their separate heads. Human milk contains 
proportionably more sugar, but does not differ in other re- 
spects. That of carnivorous animals contains caseine and 
butter, but no sugar, and corresponds to their food, which 
consists of proteine compounds and fat. 



929. Bones consist of a tissue of cartilaginous substances 
enveloping a large quantity of earthy salts. Those of adult 
animals usually afford from thirty-seven to forty-two per 
cent, of organic matter, which is principally dissolved by 
boiling water, and constitutes gelatine. The earthy matter, 
varying from fifty-eight to sixty-three per cent., is prin- 
cipally phosphate of lime. The following analyses are from 
Berzelius : 

Human Bones. Ox Bones 

Animal matter dissolved by boiling, - - 32-17 ) 33.30 
Insoluble vascular substance, - - - 1*13 ) 

Phosphate of lime with a little fluorid of calcium, 53-04 57-35 

Carbonate -of lime, 11-30 3-85 

Phosphate of magnesia, - - - - 1*16 2-05 

Soda and chlorid of sodium, - - - 1-20 3-45 



100-00 100-00 

The phosphate of lime, according to the latest researches 
of Berzelius, is the tribasic phosphate, 3CaO,P0 5 . The bones 
of infants contain comparatively less earthy matter than those 
of adults, and the same fact is observed in rickets and some 
other diseases connected with defective nutrition. 

930. The teeth have a composition very similar to bones, 
but the quantity of organic matter is less. The skeletons ot 
mollusca and of zoophytes, are composed of animal matter 
with carbonate of lime, and s nail traces of phosphates of 
lime and magnesia with fluorid of calcium. 



462 ORGANIC CHEMISTRY. 

NUTRITION OF PLANTS AND ANIMALS. 

931. The animal creation is entirely dependent for its 
support upon the products of the vegetable. Plants assimi- 
late inorganic matter, and give it a form which fits it for the 
support of animals. We may then properly consider first, 
the nutrition of vegetables. The organic substances essential 
to plants are cellulose and proteine; these enter into the 
structure of the smallest vegetable, and are necessary to the 
formation of cells, which are the first rudiments of organic 
developement. Besides these, plants may contain sugar, oils, 
acids, and resins, but these are not necessary to their con- 
stitution. 

932. The proteine compounds contain small portions of 
sulphur and phosphorus, and the ligneous fibre is never 
destitute of inorganic salts ; these are always found dissolved 
in the fluids of the plants, and are essential to its perfect 
developement. Some of them are decomposed by the plants, 
to furnish sulphur and phosphorus for the albumen and other 
proteine bodies, but beyond this, little is known of the func- 
tions of these substances. The seeds of vegetables contain 
starch and proteine, which serve for the nourishment of the 
plant until its organs are sufficiently developed to enable 
it to support itself from external sources. 

933. The food of plants consists of carbonic acid, water, 
and ammonia, in addition to the mineral salts already men- 
tioned. These are absorbed by the organs of the vegetable, 
and are converted into cellulose and proteine ; the power by 
which this is effected is unknown ; chemical affinity is con- 
trolled and directed by the agency of life so as to produce 
complex and highly organized bodies. We know, however, 
the substances which enter into combination, and the results 
of their action ; in this way the formation of these bodies 
may be expressed by formulas. 

934. The cellular tissue is formed from the elements of 
carbonic acid and water, by the separation of oxygen ; 
twelve equivalents of carbonic acid, with ten equivalents of 
water; C 12 O24+H 10 O w =C 1 2H 10 O 10 +10O ; or one equivalent 
of cellulose and ten of oxygen. In the formation of proteine, 
the elements of ammonia are added to those of carbonic acid 
and water. Forty equivalents of carbonic acid with fifteen of 
water and five of ammonia = ^ne equivalent of proteine and 
eighty-three of oxygen. It has been shown (910) that pro* 



NUTRITION OF PLANTS AND ANIMALS. 463 

teine, under certain circumstances, absorbs oxygen, and is 
decomposed into ammonia and humic acid. This last is 
formed from woody fibre, by the loss of the elements of 
water and carbonic acid ; proteine may therefore be pro- 
duced from cellulose, by adding ammonia and subtracting 
carbonic acid and water. 

935. All the other principles of plants may be formed in 
a similar manner. Starch is identical in composition with 
cellulose, and yields sugar and gum by combining with the 
elements of water. Malic acid is formed from the elements 
of eight equivalents of carbonic acid and four of water, by the 
abstraction of twelve equivalents of oxygen, and the other acids 
are produced by an analogous process. It is probable that 
the saline and alkaline matters in the sap exercise some 
influence on these processes, and conduce to the formation 
of the various products. 

936. The oxygen which is set free in all these reactions 
is evolved from the leaves in the form of gas. If a branch 
of any plant is placed under an inverted receiver, filled with 
pure water, and exposed to the sun's light, small bubbles of 
gas will appear on the leaves, which rise and collect in the 
upper part of the jar. This gas is pure oxygen, and is 
evolved by all healthy plants when exposed to the light ; in 
darkness the process of nutrition is very imperfectly per- 
formed, and the carbonic acid absorbed by roots is given off 
from the leaves unchanged. If a plant is made to grow in 
a vessel containing a mixture of common air and carbonic 
acid gas, the latter will be slowly absorbed and replaced by 
pure oxygen. Plants have the power of absorbing gaseous 
carbonic acid and water through their leaves, as well as by 
their rQots ; they also exhale large quantities of water from 
the pores on the surface of the leaves. 

937. A soil fitted for the growth of plants, must contain 
in a soluble form all the salts and mineral constituents which 
they require. These vary in different plants ; their nature 
and quantity are determined by minute analyses of the 
ashes of each vegetable. The most important are potash, 
lime, magnesia, and iron, combined with sulphuric, phos- 
phoric and silicic acids, and chlorine. Plants have the 
power to decompose these salts ; we have observed that they 
separate sulphur and phosphorus to form the proteine com- 
pounds, and all of them contain salts of potash with vegetable 
acids, as in the grape, (808.) The alkali in these has been 



464 ORGANIC CHEMISTRY. 

separated from its combination with the mineral acids ; when 
the plant is burned, these salts are decomposed, and produce 
the carbonate of potash, which the ashes of vegetables always 
contain, (505.) 

938. Many of the mineral substances are contained in the 
rocks, from whose disintegration the soil was formed, and 
their slow decomposition gradually liberates them in a 
soluble form. Often, however, by long cultivation, some 
particular ingredients of the soil become exhausted, and it is 
no longer productive. Its fertility may then be restored by 
the application of some mineral manures, as wood-ashes, or 
bone-dust. A soil which has become unfitted for the growth 
of one plant, may still contain the substances necessary to 
the support of another, and hence the utility of rotation in 
crops. The ashes of tobacco contain a large amount of 
potash, while wheat and other cereal grains abound in 
phosphate of lime ; so that a soil well adapted to the growth 
of tobacco may not be suited to wheat, and vice versa. 

939. Fertile soils generally contain, in addition to these, 
a portion of humus from the decomposition of vegetable 
matter. This is beneficial by its slow decomposition, by 
which it is constantly evolving carbonic acid, and by the 
ammonia that it contains. It thus presents a constant source 
of these substances to the roots of plants. We have stated 
that humic acid, or humus, not only combines with the 
ammonia of the atmosphere, but is able to form it by the 
direct absorption of nitrogen, (785.) Many chemists main- 
tain that humic acid itself constitutes a part of the food of 
plants, and that it combines with the elements of water and 
ammonia to generate the various products of the vegetable 
organism. This view has been ably defended, but we have 
no evidence that it is absorbed by plants, while it is certain 
it is not necessary to their growth. There are many plants 
which are capable of growing without any connection with 
the soil ; they may be suspended from the ceiling, and will 
continue to grow luxuriantly for years. In these plants the 
process of nutrition is apparently the same as in those which 
derive their support from the earth. They absorb carbonic 
acid, ammonia and water, from the atmosphere, and form 
ligneous fibre and proteine like other plants. The amount of 
mineral matter which they contain is small, and is doubtless 
derived from dust constantly floating in the atmosphere, 
which collects upon the leaves, and is dissolved and absorbed. 



NUTRITION OF PLANTS AND ANIMALS. 4-65 

We have here vegetables subsisting entirely upon the in- 
gredients of the atmosphere, and the results of experiment 
seem to show that all plants are nourished by the same 
substances, and that the only agency of humus is to afford 
carbonic acid and ammonia. 

940. From what has been stated, it is easy to understand 
why ammoniacal salts are such efficient fertilizers of the soil* 
Plants watered with a weak solution of the sulphate, or any 
other salt of ammonia, grow very rapidly, and often attain 
twice the size and strength of those growing without this 
treatment. The beneficial effects of guano and urine are 
due, in part, to the ammonia which they afford. Guano con- 
sists in the excrements of sea-birds which resort in great num- 
bers to small rocky islands on the coast of South America 
and Africa. The recent excretion consists of urate of am- 
monia, with various inorganic salts, but the uric acid is gradu- 
ally decomposed and affords oxalate of ammonia. Wheat 
manured with guano is found to contain a quantity of azotized 
matter, twice as great as that raised on the same soil without 
any manure ; this is attributable principally to the absorption 
of the ammonia. 

941. The food of both herbivorous and carnivorous ani- 
mals consists of proteine in its various forms, with starch, 
sugar, fat, and gelatine. Those subsisting on vegetables, 
appropriate the albumen and fibrine which these bodies 
contain, for the formation of muscular tissues, that finally 
become the food of carnivorous animals. The proteine 
compounds, which alone can form blood and muscle, are ob- 
viously distinguished from the non-azotized substances that 
constitute a large portion of the food of many animals. 
Liebig conveniently designates them as the Elements of Nu- 
trition, while gelatine and all non-azotized food are called 
Elements of Respiration, as they are supposed to be in a 
great measure consumed in that process. 

942. The nature of the digestive process has been already 
noticed, (920.) The substances taken as food are reduced 
by the fluids of the stomach to a state of solution. They 
then pass into the small intestines, where the lacteals take up 
the portions which have been rendered soluble, and fitted for 
the purposes of nutrition. The saccharine and farinaceous 
portions of the food have never been observed in the chyle, 
but the blood, shortly after the saccharine substances have 
been taken into the stomach, contains a very appreciable 



466 



ORGANIC CHEMISTRY. 



quantity of them. It is well known that water and saline 
fluids are directly absorbod by the blood-vessels of the 
lining membrane of the stomach, and it is probable that 
alimentary substances in a state of complete solution are 
taken into the circulation in the same manner. These soon 
disappear from the blood, and are supposed to be oxydized 
in the lungs. 

943. The non-azotized matters taken into the stomach are 
probably in part converted into fat. The most complete and 
satisfactory experiments have proved, that fat is really formed 
in the system, and is not, as was formerly supposed, derived 
from that contained in the food. Geese fed upon corn, are 
found to secrete an amount of fat much greater than is con- 
tained in the maize eaten by them, and bees form wax if fed 
upon sugar. We are indeed able to form one of the fatty 
acids of butter, (butyric acid,) from starch or sugar by fer- 
mentation. It is only by supposing it to be formed in the 
alimentary process, that we can account for the constant pre- 
sence of fat in the chyle. 

The proteine compounds in the chyle require merely the 
organizing power of the vital force to give them the form of 
muscular tissue. 

944. In the living body there is a constant waste of the 
tissues; the chemical forces, aided by the agency of the 
oxygen of the air, are producing a transformation of the mus- 
cular and adipose substances into simpler products, which 
are excreted from the body in various ways. Baron Liebig 
has shown that a simple relation exists between the compo- 
sition of the muscular fibre and the elements of the bile and 
urine ; so that choleic acid and urea may be formed from it, 
by the addition of a little oxygen. The urea and uric acid 
contain the more azotized portions, and the bile those which 
are rich in carbon. The fatty tissues on the contrary appear 
to be completely converted into carbonic acid and water. 
The object of nutrition is to preserve the equilibrium of the 
system by supplying the waste of the tissues, and so long as 
this balance is maintained, the organism is in a healthy con- 
dition. When the amount of non-azotized food is greater 
than is consumed in the process of respiration, the excess is 
secreted in the form of fat, and sometimes increases to an 
enormous extent, as is seen in the fattening of domestic 
animals. If, however, the supply is stopped, the reverse 



NUTRITION OF PLANTS AND ANIMALS. 46? 

process commences ; the secreted fat is taken into the system 
and oxydized, and as there is no way to supply its loss, is 
soon completely absorbed. 

945. The act of respiration has for its object to bring the 
blood into contact with the oxygen of the atmosphere. In 
the higher orders of animals, this is accomplished through 
the lungs. These organs have a cellular structure, and are 
composed of a great number of cavities capable of inflation 
with air. Over the surfaces of these are spread the minute 
branches of the pulmonary artery, and the blood is conse- 
quently brought into close contact with the air. In the pro- 
cess oxygen gas is absorbed, and carbonic acid gas expelled. 
The relative proportions which the oxygen absorbed, and the 
carbonic acid exhaled, bear to one another, are determined by 
the law of the mutual diffusion of gases already mentioned, 
(132.) By this law, the volumes of any two' gases which 
pass through a porous medium to mingle with each other, 
will be in the inverse proportion of the square roots of their 
specific gravities. The volume of oxygen that passes inward, 
will exceed that of the carbonic acid which passes outward, 
in the proportion of 1174 to 1000. As carbonic acid contains 
exactly its own volume of oxygen, it follows that 174 parts 
or nearly fifteen per cent, more of oxygen are absorbed by 
the lungs than are given out in the form of carbonic acid. 
A portion of this excess of oxygen unites with the sulphur 
and phosphorus of the original components of the body, con- 
verting them into sulphuric and phosphoric acids, and the 
remainder probably combines with the hydrogen of the fatty 
matter to form part of the water which is exhaled from the 
lungs. 

946. The changes produced upon the blood by respiration 
have been already described, (917.) This process is essential 
to life, and even in the lower orders of marine animals, is 
effected through the aid of oxygen dissolved in the water. 
Experiments have shown that the amount of carbon given 
off from the lungs by a full-grown man, is about seven 
ounces in twenty-four hours. This oxydation, or slow com- 
bustion of carbon, must necessarily evolve heat, and is doubt- 
less one source of the heat of the animal system ; but the 
temperature of living animals is due in part to the other 
changes which are going on in the organism. In some cases 
of disease, when the respiratory function has been almost 



468 ORGANIC CHEMISTRY. 

entirely suspended for hours, the temperature of the body 
has remained undiminished. 

947. Vegetables have to a certain extent the power of 
maintaining a temperature above that of the atmosphere ; 
this is particularly observed in the leaves and young shoots, 
where vegetation is most active. In the flowering of some 
species of Arum, a thermometer placed among the spadices 
has been observed to rise to 121°, when the temperature of 
the atmosphere was only 66°. Experiments have shown that 
in this case it is due to the absorption of oxygen, but it is 
hardly probable that such is the general cause. When we 
consider that heat is evolved in very many changes which 
are often independent of the absorption of oxygen, there is 
no difficulty in accounting for its production in the processes 
of nutrition and assimilation. 

948. It is, however, true that in health, the oxydation of 
carbon may be taken as a measure of the heat evolved. 
The inhabitants of Greenland and other northern countries 
consume in their food immense quantities of fat and oil, and 
voyagers in these regions, have found such a diet not only 
healthful, but even necessary, to enable them to endure the 
intense cold to which they were exposed. 

949. In those animals which subsist entirely upon flesh, 
the amount of oxygen absorbed is not less than in the herbi- 
vorous, and the oxydizing process is at the expense of the 
muscular tissue. The waste of this is consequently much 
greater than in those animals subsisting upon a mixed diet, 
the fat and starch of which supply the demands of the 
respiratory process. 

950. The lifeless particles of the inorganic world are 
assimilated by plants from the atmosphere, the soil, and the 
waters. Once taken into their structure, they are trans- 
formed by the vital force into woody fibre, starch, sugar, and 
proteine, which afford the materials for the nutrition of 
animals, and supply the constant demand of the respiratory 
functions. By the regular processes of life these are again 
set free in their original forms of carbonic acid, ammonia, 
and water, and are once more ready to enter the upward 
current of organic life. 

By a beautiful adjustment of these organic forces, the 
balance of the two great kingdoms of nature is maintained. 
The carbonic acid set free by the processes of combustion, 



NUTRITION OF PLANTS AND ANIMALS. 469 

and the respiration of animals, fails to vitiate the purity of 
the atmosphere, because the vegetable kingdom appropriates 
all the carbon of this gas for its own support, and restores 
an equal volume of pure oxygen to the air. 

The mind rests with equal pleasure and admiration on 
these beautiful laws, which silently, but unceasingly, work 
out an expression of the Almighty Will. 

40 



INDEX. 



*** The references are to the numbers of the sections 



Acetates, 725. 

Acetene, 710. 

Acetone, 733. 

Acetic acid, quick process for, 722. 

Acetic ether, 732. 

Acetic amylic ether, 743. 

Acid, acetic, 720; acetonic, 814; 
aconitic, 816; adipic, 803; an- 
amirtic, 800 ; antimonic, 624 ; 
antimonious, 624 ; arsenic, 629 ; 
arsenious, 628 ; benzoic, 755 ; 
boracie, 370 ; bromic, 274 ; bu- 
tyric, 794 ; capric, caproic, ca- 
prylic, 795 ; carbazotic, 763 ; 
carbolic, 763 ; carbonic, 339 ; 
carbovinic, 713 ; cerebric, 927 ; 
chloracetic, 731 ; chloric, 271 ; 
chlorochromic, 595 ; chlorous, 
269; choleic, 922; chromic, 
593 ; cinnamic, 764 ; citraco- 
nic, 816; citric, 815; cocinic, 
797 ; columbic, 612 ; cyanic, 
874 ; cuminic, 758 ; cyanuric, 
886; dialuric,900; elaidic,802; 
enanthylic, 795 ; ethalic, 750 ; 
equicetic, 814 ; ferric, 587 ; 
ferridcyanic, 888 ; ferrocyanic, 
886; fluoboric, 373 ; fluosilicic, 
364 ; formic, 741 ; fulminic, 
872; fumaric, 814; gallic, 819; 
hippuric, 903 ; humic, 785; hy- 
driodic,423; hydrobromic,422; 
hydrochloric, 416; hydrocya- 
nic, 867 ; hydrofluoric, 425 ; 
hydroselenic, 436 ; hydrosul- 
phuric, 429; hyperiodic, 278; 
hypochlorous, 267 ; hydrotellu- 
ric, 436; hyponitrous, 310; hy- 
pophosphorous, 320 ; iodic, 278; 



isatinic, 839; kinic, 850; lac- 
tic, 772; lauric, 797; malic, 
813; maleic, 814; manganic, 
577 ; margaric, 798 ; meconic, 
852 ; metacetonic, 776 ; molyb- 
dic, 612 ; mucic, 777 ; muria- 
tic, 416 ; myristic, 797 ; nitric, 
312; nitrobenzoic, 755; nitro- 
muriatic,420; nitrophenisic,ni- 
tropicric,763;nitrosalicylic,762; 
nitrous, 311; oleic, 802; opianic, 
852; osmic,737; oxalic,806; ox- 
alovinic, 808 ; oxaluric, 902 ; ox- 
amic,807 ; parabanic,902 ; para- 
taric,810; pectic,778; pelargo- 
nic, 795 ; permanganic, 577 ; 
phosphoric, 324 ; picric, 763 ; 
pimelic,803; phosphovinic,713; 
platinocyanic,8S9 ; prussic,867 ; 
pyroligneous,723 ; racemic,812; 
saccharic, 775 ; salicylic, 760 ; 
sebacic, 803; selenic, 298; se- 
lenious, 298; silicic, 359; stan- 
nic, 615; stearic, 799; suberic, 
succinic,803; sulphamylic,744 ; 
sulphethalic, 748 ; sulphovinic, 
711; sulphindigotic, 838; suL 
phocetic, 748 ; sulphocyanic, 
880 ; sulphomethylic, 737 ; sul- 
phurous, 286 ; sulphuric, 289 ; 
tannic, 817 ; tartaric, 810 ; tar- 
tarovinic, 811 ; telluric, tellu- 
rous, 299; titanic, 612; tung- 
stic, 612; ulmic, 785; uric,89S; 
valeric (valerianic), 746; xan- 
thic, 713. 
Acids and alcohols, compared,702 ; 
fatty, list of, 801; vegetable, 
805. 



J.72 



INDEX. 



Acids, 195; coupled, 704; named, 
] 98 ; monobasic, 674 ; vinic, 
703; theory of, 485. 

Aconitine, 855. 

Acroleine, 791. 

Affinity, chemical, 206; circum- 
stances which influence, 209. 

Agriculture, chemistry of, 937. 

Air-pump, 28. 

Air, analysis of, 303. 

Albumen, animal, 908 ; vegetable, 
906. 

Alcohol, 699 ; products of its 
oxydation, 719; amylic, 742; 
methylic sulphur, 701. 

Alcohols and acids, relations of, 
702. 

Aldehyde, 719. 

Algaroth, powder of, 625. 

Alizarine, 830. 

Alkaloids, 843 ; of Peruvian bark, 
850; of opium, 851. 

Alcargene, 897; Alcarsine, 894. 

Allantoine, 899. 

Allotropism, 264. 

Alloxan, 899; Alloxantine, 900. 

Alloys, 477. 

Almonds, essential oil of bitter, 
753. 

Alumina, 567 ; acetate of, 725 ; 
silicates of, 570 ; sulphate of, 
568. 

Aluminium, 566. 

Alum, 568. 

Amalgams, 639; Amalgamation, 
161. 

Amarine, 849. 

Ammeline, 883. 

Amides, 697. 

Ammonia, 438 ; acetate of, 725 ; 
bin-iodized, 695; hydrosulphu- 
ret of, 538; oxalate of, 698, 
807 ; present in the atmosphere, 
439 ; trichlorinized, 395 ; salts 
of ammonia, 537 ; water of, 
442 ; use of as a fertilizer, 940. 

Ammonium, 536 ; salts of, 537 ; 
chlorid of, sulphuret of, 538; 

Ampere's theory, 168; — rotating 
battery, 173. 

Amygdaline, 859. 

Amylic ether, 745. 



Amylic alcohol, products of its 
oxydation, 745. 

Amylol, 742. 

Amylether, 745. 

Amarine, 754. 

Analysis of organic bodies, 682. 

Anhydrous sulphuric acid, 294. 

Anilene, 844, 846. 

Animals, nutrition of, 931 ; food 
of, 941. 

Anthracite, 786. 

Antimony, 622 ; compounds with 
oxygen, 623 ; chlorids of, 625 ; 
glass of, 623 ; sulphurets of, 
626 ; tartrate of, and potash, 
811. 

Aqua regia, 420 ; ammoniac, 442 ; 
fortis, 314. 

Araeometer of Nicholson, 42. 

Arbor, Dianae, 651 ; Saturni, 605. 

Argol, 810. 

Aricine, 850. 

Arsenic, 627 ; as a poison, de- 
tection of, 632 ; chlorids of, 
630 ; compounds of, with oxy- 
gen, 628 ; Marsh's test for, 636 ; 
reduction of, 634 ; salts of, 629 ; 
sulphurets of, 630. 

Arseniureted hydrogen, 631. 

Arsine, 895. 

Artesian wells, 70. 

Asparagine, 860. 

Assafcetida, oil of, 826. 

Atmosphere, chemical history of, 
302 ; mechanical properties of, 
24; weight of, 31, 32; deter- 
mination, pressure of, 34 ; limits 
of, 35. 

Atomic theory, 213; weights, 
table of, 188. 

Atoms, 8; specific heat of, 215; 
polarity of, 218. 

Attraction of gravitation, 8 ; che 
mical, 12. 

Atropine, 854. 

Aurum Musivum, 617. 

Azote, see Nitrogen, 300. 

Balance, 37; of organic forces, 950. 

Barium, 544 ; chlorid of, 546. 

Barometer, 33. 

Baryta, 545; carbonate of, 548; 
nitrate of, 547 ; sulphate of, 5 17. 



473 



Batteries, galvanic, 164 ; sustain- 
ing, 244 ; DaniePs, 245 ; Smee's, 
247. 

Beeswax, 800. 

Benzamide, 754 ; Benzoine, 756.. 

Benzene, or Benzole, 757. 

Benzoline, 754. 

Benzeline, 846. 

Benzoilol, 753 ; chlorinized, 754 ; 
sulphureted, 753. 

Bile, 922. 

Bibasic acids, 674. 

Bismuth, 618 ; oxyd of, 619 ; ni- 
trate of, 620 ; fusible alloy, 621. 

Bituminous coal, 786. 

Bleaching powders, 559. 

Blood, 915. 

Blowpipe, compound, 400; mouth, 
468. 

Blue pill, 639. 

Boiling, phenomena of, 119; boil- 
ing-point, 119; elevated by 
pressure, 125. 

Bones, 929. 

Boracic ether, 714. 

Boron, preparation and properties, 
368; compound with oxygen, 
369 ; chlorid of, 372 ; fluorid of, 
373 ; sulphuret of, 374. 

Borax, 532. 

Brain and nervous matter, 927. 

Bread-making, 907. 

British gum, 779. 

Bromine, history and preparation 
of, 272. 

Brucine, 853. 

Butter and butyrine, 794. 

Butyrone, 794. 

Cadmium, 601. 

Caffeine, 856. 

Calcium, properties of, 551 ; chlo- 
rid of, 554 ; fluorid of, 556 ; 
oxyd of, 552. 

Calculi, urinary, 926. 

Calomel, 641. 

Camphene, 821. 

Camphor, 824 ; artificial, 820 ; 
Borneo, 825. 

Cane sugar, 766. 

Caoutchouc, 827. 

Capacity for heat, 106. 

Capillary attraction, 21. 
40* 



Capsicine, 855. 

Caustic potash, 493. 

Carbonic acid, liquefaction and 
solidification of, 137 ; how re- 
moved from wells, 344 ; of at- 
mosphere, 345. 

Carbonic oxyd, 347. 

Carthamine, 830. 

Carbureted hydrogen, heavy, 454. 
" " light, 451. 

Carmine, 830. 

Carbon, properties and history, 
330; bisulphuret of, 352; chlo- 
rids of, 351 ; compounds with 
hydrogen, 449; nitrogen, 354; 
compounds with oxygen, 338 ; 
oxyd of, 347 ; density of vapor 
of, 680. 

Caseine, 909 ; vegetable 906. 

Cathode, 236. 

Catalysis, 212. 

Cassius, purple of, 655 

Cellular tissue, formation of, 934. 

Cellulose, 781. 

Cerium, 573. 

Cetene, 749. 

Chameleon mineral, 577. 

Charcoal, 335 ; absorbs gases, 336 ; 
and odors, 337. 

Chlorophyle, 831. 

Chemical affinity, 206; attraction, 
12; nomenclature, 193; philo 
sophy, 182. 

Cinchona bark, 850. 

Cinnamol, 764. 

Cinchonine, 850. 

Chloranile, 842. [845. 

Chloranilene and bichloranilene, 

Chlorarsine, 895.. 

Chloric ether, 739. 

Chlorine, preparation ana proper- 
ties, 260 ; allotropism of, 264 ; 
compounds with oxygen, 266. 

Chlorisatine and bichlorisatine, 
841. 

Chloroform, 739. 

Chlorophyle, 831. 

Cholesterine, 922. 

Chondrine, 913. 

Chromium described, 590; chlo- 
rids of, 592; compounds with 
oxygen, 591; salts of, 594. 



474 



INDEX. 



Cinnamol, 764. 

Chyle, 919. 

Classification of elements, 250. 

Cleavage of crystals, 227. 

Coal, 334, 786; gas from, 457; 
products of its distillation, 786. 

Coal tar, 789. 

Cobalt, described, 598 ; chlorid of, 
598. 

Codeine, 852. 

Cohesion, 10 ; of fluids, 22. 

Color of bodies, 61. 

Coloring matters described, 829 ; 
red, 830; from lichens, 832; 
yellow, 829. 

Columbium and columbite, 612. 

Compound electro-magnetic ma- 
chine, 178. 

Compounds, named, 195. 

Combination, mode of, in organic 
bodies, 669. 

Combination, kws of, 184; by 
volume, 190. 

Combustion, a source of heat, 70 ; 
nature of, 461; heat of, 462; 
and structure of flame, 459. 

Congelation, 109. 

Conine, 846. 

Convection of heat, 94. 

Copper, described, 608; acetate 
of, 730 ; alloys of, 614 ; nitrate 
of, 611; oxyds of, 609; sul- 
phate of, 610. 

Cotarnine, 852. 

Corrosive sublimate, 641. 

Coupled acids, 704. 

Cream of tartar, 811. 

Cryophorous, 123. 

Crystallization, circumstances in- 
fluencing it, 217; nature of, 216. 

Crystals, measurement of, 228; 
primary forms, 220. 

Cupellation, 648. 

Cyanates, 874. 

Cyanids, 866 ; complex, 884 ; dou- 
ble, 867. 

Current, passage of in cells of a 
battery, 241. 

Cyamelide, 875. 

Cyanogen, 354, 872 ; compounds 
with bromine, chlorine, &c, 
871 ; hydrogen, 873. 



Cyanoxsulphide, 880. 

Daniell's battery, 245. 

Davy's safety lamp, 470. 

Decomposition of water, 235, 386. 

De La Rive's ring, 170. 

Density of vapours, 131, 680, 37. 

Dew, formation of, 99 ; point, 133. 

Dextrine, 779. 

Diabetic sugar, 767. 

Diamond, history and forms of, 
331. 

Diachylon, plaster, 804. 

Diastase, 780, 907. 

Didymium, 573. 

Diffusion of gases and vapours, 
132. 

Digestive process, nature of, 920. 

Dimorphism, 233. 

Dipping needle, 143. 

Direct union, 677. 

Distillation, 117; of alcohol, 699. 

Dryabalanops, 825. 

Du Fay's hypothesis, 150. 

Drummond light, 403. 

Dutch liquid, 454, 718. 

Earth's magnetism, 143. 

Elaldehyde, 720. 

Elasticity, 18 ; of air, 26. 

Electrical machine, 153. 

Electrical excitement, 147; po- 
larity, 148. 

Electricity, conductors of, 151 ; 
of high steam, 156 ; theories of, 
150. 

Electricity of chemical action, 
158. 

Electro-chemical decomposition, 
234 ; conditions of, 237 ; mag- 
netism,^; magnetic telegraph, 
179; metallurgy, 248. 

Electro-magnetic motions, 173. 

Electro-magnets, 171. 

Electrolysis, 237 ; order of, 240. 

Electrode, 237. 

Electrophorus, 155. 

Electroscopes, 152. 

Elements, defined, 14 ; laws of 
combination and classification, 
250, 182 ; non-metallic, classi- 
fied, 250. 

Emetic, tartar, 811. 

Emetine, 855. 



INDEX. 



475 



Emulsine, 859. 

Epsom salts, 563. 

Equivalents, table of, 188. 

Equivalent proportions, 187. 

Equivalent substitution, 670. 

Eremacausis, 785. 

Ethal, 748. 

Ether, acetic, 732 ; acetic amylic, 
743; benzoic, 715; boracic, 
714 ; butyric, 794 ; chloric, 739 ; 
hydrobromic, 709 ; hydrochlo- 
ric, 708; hyponitrous, 710; lu- 
miniferous, 51 ; methylic, 738; 
nitric, 706; nitrous, 710; ox- 
alic, 703 ; perchloric, 707 ; si- 
licic, 714; sulphuric, 715. 

Ethers, 702 ; sulphureted, 716. 

Equilibrium of temperature, 89. 

Euchlorine, 267. 

Eudiometry, 303 ; by hydrogen, 
395. 

Eupione, 788. 

Evaporation, 129. 

Expansion by heat, 71 ; of solids 
and liquids, 28, 73, 74 ; of gases, 
88 ; of water, 86 ; beneficial 
results of, 87. 

Faraday's researches in magnet- 
ism, 145 ; in liquefaction, 136 ; 
in electricity, 236. 

Fats and substances derived from 
them, 791. 

Fattening animals, 943. 

Feldspar, 570. 

Fermentation, viscous, 772; vi- 
nous, 770. 

Ferridcyanogen, 887. 

Ferrocyanogen, 885. 

Fertilizers, 938, 940. 

Fibre, woody, 781. 

Fibrine, animal and vegetable, 
906, 908. 

Fire damp, 451. 

Flame, structure of, 459, 464; 
effects of wire gauze on, 469. 

Fluorine, history and properties, 
280. 

Fluor spar, 556. 

Fluids, properties of, 19. 

Formates, 741. 

Formene, tri-chlorinized and tri- 
iodized, 739. 



Franklinian hypothesis, 150. 

Freezing mixtures, 111. 

Friction a source of heat, 70. 

Fulminates, 892. 

Fusel oil, 742. 

Fusible metal, 621. 

Galena, 602. 

Galleide, 819. 

Gall-nuts, 817. 

Galvanism, 158; origin and dis- 
covery of, 159 ; quantity and 
intensity in, 163. 

Galvanic batteries, 164, 244. 

Galvanoscopes, 167. 

Gases, laws of, 24; liquefaction 
of, 136 ; management of, 257 ; 
combine by volume, 190 

Gasholders, 258. 

Gastric juice, 920. 

Gelatine, 913. 

Geine, 785. 

German silver, 597. 

Glass, 534. 

Glucinum, 573. 

Glucose, 767. 

Gluten, 906. 

Glycerides, 792. 

Glycerine, 791. 

Glycocoll, 903. 

Gold, 652 ; oxyds and chlorid of, 
654. 

Gold wash, 655. 

Goniometer, common, 228 ; Wol- 
laston's, 229. 

Goulard's extract, 727. 

Grape sugar, 767; fermentation 
of, 770. 

Graphite, 333. 

Grove's battery, 246. 

Gum, 777 ; elastic, 827. 

Gun cotton, 784. 

Gunpowder, composition of, 513. 

Gutta percha, 828. 

Gypsum, 555. 

Hardness, 18. 

Hare's blowpipe, 400. 

Hare's deflagrator, 164. 

Heat, 69 ; communication of, 89 ; 
absorption of, 101; convection 
of, 94; conduction of, 90; ex- 
pansion by, 71, 82 ; radiant, 97 ; 
sources of, 70 ; specific, 106 ; 



476 



INDEX. 



transmisson of, 103 ; latent, 
108. 

Heavy spar, 547. 

Helicine, 864. 

Helix, 169. 

Hematine, 916. 

Hematite, red and brown, 582. 

Hematoxyline, 830. 

Hemming's safety tube, 402. 

Henry's coils, magnets, 171, 175. 

Homologous bodies, 751. 

Humus, 785. 

Hydrobenzamide, 754. 

Hydrosalimide, 759. 

Hydrochloric amylic ether, 743. 

Hydrochloric methylic ether,.735. 

Hydrogen, preparation and pro- 
perties, 375; nature of, 383; 
acids of, 413; action with chlo- 
rine, 414 ; arseniureted, 631; 
compound with boron, 458; bro- 
mine, 422 ; carbon, 449 ; chlo- 
rid, 416 ; fluorine, 425 ; iodine, 
423 ; nitrogen, 437 ; oxygen, 
384; phosphorus, 445; seleni- 
um, 436; sulphur, 429; per- 
oxyd of, 410. 

Hydrometer, 47. 

Hydrosulphuret of ammonium, 
538. 

Hygrometers, 134. 

Hypochlorite of lime, 559. 

Imponderable agents, 15. 

Indigo, 835. 

Indigogene, 837. 

Induction of a current on itself, 
175. 

Induction of magnetism, 140. 

Ink, black, 817 ; blue, 886. 

Insulators of electricity, 151. 

Intensity, quantity, 163. 

Induced currents, 177. 

Induction of electricity on tele- 
graph wires, 179. 

Iodiform,.739. 

Iodine, 275 ; acetate of, 725 ; com- 
pounds with oxygen, &c, 278. 

Ions, 236. 

Iridium, 661. 

Iron, 580 ; carbonate of, 589 ; fer- 
rocyanid, 885 ; ores of, 582 ; 
lactate of, 774 ; oxyds of, 585 ; 



reduction of its ores, 583 ; salts 
of, 589 ; specular, 586 ; sulphu- 
rets of, 588. 

Isatine, 839 ; isatyde, 841. 

Isomerism, 678. 

Isomorphism, 231. 

Kakodyle, 896 ; protoxyd of, 897. 

Kermes mineral, 626. 

Kreasote, 787. 

Kyanite, 570. 

Kyanizing process, 641. 

Kyanol, 789. 

Lactates, 774; lactide, 774. 

Lactine, 768. 

Lamp, Davy's safety, 470; Jack 
son's, 467. 

Lantanum, 573. 

Laughing gas, 305. 

Lard oil, 804. 

Lead, 602 ; acetate of, 726 ; car- 
bonate of, 606, 728 ; chromate 
of, 595 ; oxyds of, 603 ; plaster 
or diachylon, 804 ; precipitated 
by zinc, 605 ; sulphuret, 604. 

Leather, 913. 

Lecanorine, 833. 

Legumine, 906. 

Leiocome, 779. 

Letheon, 715. 

Leyden jar, 154. 

Leukol, 789, 846. 

Lichens, 832. 

Light, 50 ; properties of, 52 ; la 
tent, 66 ; sources and nature, 51 ; 
analysis of, 59 ; chemical rays, 
65. 

Lignine, 781. 

Lignite, 785. 

Lime, 552 ; butyrate of, 774, 775 ; 
carbonate of, 558; chlorid of, 
559 ; lactate of, 774 ; oxalate 
of, 808 ; phosphates of, 557 ; sul- 
phate of, 555. 

Liquefaction, 108; and solidifica- 
tion of gases, 137. 

Liquids, properties of, 20. 

Lithium and lithia, 543. 

Litmus, 832. 

Local action, 244. 

Lodestone, 139. 

Lunar caustic, 651. 

Luteoline, 829. 



INDEX. 



477 



Lymph, 919. 

Magic circle, 172. 

Magnesia, 560 ; carbonate of, 564 ; 
sulphate of, 563. 

Magnesium, 560 ; chlorid of, 562 ; 
oxyd of, 561. 

Magnetism, 139 ; Magneto-elec- 
tricity, 180. 

Magnetics and diamagnetics, 145. 

Magnets, 141. 

Magnets, electro, 171. 

Malachite, green and blue, 608. 

Malt, action of on sugar, 780. 

Malates, 813. 

Manganese, 574 ; chlorids of, 578 ; 
oxyds of, 575 ; salts of 579. 

Mannite, 769. 

Marble, 558. 

Margarine, 798. 

Marriotte's law, 30. 

Marsh gas, 451. 

Marsh's test for arsenic, 636. 

Matter, general properties of, 6 ; 
states of, 16. 

Melting-points, 112. 

Mellon, 880. 

Melloni's researches, 104. 

Melam, 880. 

Melamine, 883. 

Mercaptan, 701. 

Mercury, 638 ; double amide of, 
646 ; chlorids of, 641 ; amide of, 
646; cyanid of, 871 ; fulminate 
of, 892 ; iodids of, 642 ; nitrates 
of, 644 ; oxyds of, 640 ; sulphate 
of, 645 ; sulphurets of, 643. 

Metacetone, 776. 

Metameric bodies, 678. 

Metaldehyde, 720. 

Metallurgy, electro, 248. 

Metals, general properties of, 472 ; 
oxyds of, 479; chemical rela- 
tions of, 478 ; classification of, 
487 ; tenacity of, 474. 

Methal, 734. 

Methylic alcohol, 734. 
Methylic ether, 738. 
Methen, 738. 
Microscomic salt, 529. 

Milk, 928; sugar of, 768. 
Mindereus, spirit of, 725. 
Molecules, 8; polarity of, 218. 



Molybdenum, 612. 

Monobasic acids, 674. 

Mordants, 569. 

Morphine, 851. 

Mouth blowpipe, 468. 

Murexide, 901. 

Muriatic acid, 416. 

Mustard, oil of, 826. 

Names of elements, 193. 

Nascent state, 210. 

Naphtha, 790 ; naphthaline, 789. 

Narcotine, 852; narceine, 852. 

Nervous matter, 927. 

Neutrality of salts, 483. 

Newton's fusible metal, 621. 

Nickel and its oxyds, 596; sul- 
phate, 597. 

Nicotine, 847, 

Nitre, 511. 

Nitric methylic ether, 735. 

Nitrobenzene, 757. 

Nitrogen, 300 ; compounds with 
oxygen, 304; determined in 
organic compounds, 690. 

Nitrous oxyd, 305. 

Nitric oxyd, 308. 

Nitranilene, 845. 

Nomenclature and symbols, 193. 

Nordhausen acid, 292. 

Nutritive substances, 905. 

Nutrition of plants and animals, 
931 ; elements of, 941. 

(Ersted's law, 166. 

Oil of bitter almonds, 753 ; of 
mustard, 826; of roses, 823; 
lard, 804; palm, 797; potato, 
742 ; of cumin, 758 ; of cinna- 
mon, 764; of the Dutch che- 
mists, 718; spirea, 759; tur- 
pentine, 821 ; wintergreen, 761. 

Oils, volatile or essential, 820. 

Olefiant gas, 454, 717 ; with chlo- 
rine, 456. 

Oleine, 802. 

Opium, 851. 

Orceine, 833. 

Organic bases or alkaloids, 843. 

Organic bodies characterized, 666 ; 
general properties of, 662 ; ana- 
lysis of, 663 ; modes of com- 
bination in, 669. 

Organic nature, balance of, 950. 



478 



INDEX. 



Orpiment, 630. 

Osmium, 637. 

Oxygen, 252. 

Oxamide, 698. 

Oxamethane, 809. 

Oxalates, 807. 

Oxalic methylic ether, 809. 

Ozone, 412. 

Page's revolving armature, 174. 

Palm oil, 797. 

Palmatine, 792. 

Palladium, 659. 

Pancreatic fluid, 921. 

Paranaphthalene, 789. 

Paraffine, 788. 

Peat, 786. 

Pendulums, 84. 

Peruvian bark, 850. 

Pepsine, 920. 

Petalite, 570. 

Petroleum, 790. 

Phenol, 763. 

Phloretine, 865. 

Phloridzine, 865. 

Phocenine, 795. 

Phosgene gas, 349. 

Phosphorescence, 68. 

Phosphorus, 376; chlorids, bro- 
mids, &c, 326 ; compounds with 
oxygen, 320 ; 

Phosphureted hydrogen, 445. 

Plants, their nutrition, 933. 

Platinocyanids, 889. 

Platinum, 656 ; chlorids and oxyds, 
658 ; power to cause the union 
of gases, 397 ; sponge and black, 
657. 

Plumbago, 333. 

Polarization of light, 63. 

Polarity, electrical, 148, 163. 

Polar attractions in electrolysis, 
238. 

Polymeric bodies, 679. 

Potash, 493 ; acetate of, 725 ; 
carbonates of, 505, 507; chlo- 
rate, 515 ; chromate of, 594 ; 
cyanate, 876 ; nitrate, 511 ; salts 
of, 504 ; sulphates of, 508 ; tar- 
trate of, 811 ; yellow prussiate, 
885 ; red prussiate, 886. 

Potassium, 488, 492 ; chlorid, bro- 
mid, &c, 497; cyanid, 867; 



compound with nitrogen, 503 ; 

ferridcyanid of, 887 ; ferrocy- 

anid, 885 ; oxyds of, 493 ; sul- 

phocyanid, 880. 
Potato oil, 742. 
Pottery, art of, 571. 
Pneumatic trough, 257. 
Presence of a third body, 212. 
Prussian blue, 886. 
Prussic acid, 867, 885. 
Prussiate of potash, 885, 887. 
Prism, its action on light, 58. 
Prismatic colors, 60. 
Proteine, 910 ; relation to fibrine, 

911. 
Pseudomorphine, 852. 
Ptyaline, 921. 
Purple of Cassius, 655. 
Pyrometer, 81. 
Pyroxylic spirit, 734. 
Pyroxyline, 784. 
Quantity and intensity, 163. 
Quercitrine, 829. 
Quicksilver, 638. 
Quinine, 850 ; quinoline, 846. 
Radicals, salt, 485. 
Ratsbane, 628 ; realgar, 630. 
Red lead, 604 ; precipitate, 640. 
Reflection and refraction of light, 

54, 55. 
Refraction, double, 62. 
Rennet, 909. 
Repulsion, 11. 

Residues of substitution, 675. 
Resin gas, 457. 

Respiration, 945; elements of, 941. 
Rhodium and its compounds, 660. 
Rochelle salt, 811. 
Safety lamp, 470. 
Sal ammoniac, 439, 537. 
Salicine, 861. 

Salicylol and its derivatives, 759. 
Salicylic methylic ether, 761. 
Saligenine, saliretine, 862. 
Saliva, 921. 
Salts, theory of, 484 ; neutrality 

of, 483. 
Salt, common, 521. 
| Salt-radical, 485. 
I Saltpetre, 511. 
j Sanguinarine, 855. 
I Saxon blue, 838. 



INDEX. 



479 



Secondary currents, 176. 

Selenium, 296 ; oxyd of, 298. 

Seleniureted hydrogen, 436. 

Serum, 915. 

Sesqui-salts, 676. 

Silica, 359. 

Silicic ethers, 714. 

Silicon, 355; compounds of, 358; 
chlorid of, 363 ; rluorid of, 364 ; 
sulphuret, 366. 

Silver, 647 ; oxyds of, 649 ; chlorid 
of, 650 ; nitrate of, 651 ; acetate 
of, 730 ; cyanid of, 890 ; fulmi- 
nate of, 893. 

Smee's battery, 247. 

Soaps, 791, 804. 

Soda, 520; acetate of, 725; bibo- 
rate of, 532 ; carbonate of, 
523 ; nitrate of, 527 ; phosphates 
of, 528; silicates of, 533; sul- 
phate of, 525. 

Sodium, 518; chlorid of, 521. 

Soils, relation of to plants, 937. 

Solanine, 854. 

Solids, properties of, 17 ; expan- 
sion of, 82. 

Solution, 208. 

Spathic iron, 589. 

Specific gravity, 38 ; rule for, 42 ; 
of gases, 49. 

Specific heat of bodies, 106. 

Spectral impressions, 67. 

Spermaceti, 749. 

Spheroidal state of bodies, 135. 

Spirea ulmaria, oil of, 759. 

Spirit, pyroxylic, 734. 

Starch, 779. 

Steam, 125; latent heat of, 118; 
elastic force of, 126; engine, 
128. 

Stearine, 798. 

Stearoptens, 824. 

Steel, 584. 

Strontia, 549 ; salts of, 550. 

Strontium, 549; chlorid of, 550. 

Strychnine, 853. 

Substitution, equivalent, 670. 

Substitution by residues, 675. 

Succinide, 803. 

Sugar of lead, 726. 

Sugar of milk, 768. 

Sugars, 765 ; products of their de- 
composition, 770. 



Sulphamethylane, 736. 

Sulphisatine, 841. 

Sulphovinates, 705. 

Sulphovinic acid, products of its 
decomposition, 715. 

Sulphocyanates, 880. 

Sulphur, 282 ; compounds with 
oxygen, 285 ; chlorid of, 295. 

Sulphureted hydrogen, 429. 

Sulphuric methylic ether, 736. 

Surbasic and bisurbasic acetate of 
lead, 726, 727. 

Sustaining batteries, 244. 

Symbols, chemical, 203. 

Synaptase, 859. 

Table of chemical equivalents, 188. 

Tannin, 817. 

Tartar emetic and tartrates, 811. 

Taurine, 923. 

Telegraph, electro-magnetic, 179. 

Tellureted hydrogen, 436. 

Tellurium, 299. 

Temperature of flame, 465; of 
incandescence, 463 ; equilibri- 
um of, 89. 

Thebaine, 852. 

Theine, 856 ; theobromine, 857. 

Theories of electro-chemical de- 
composition, 243; of electro- 
chemical action, 243 ; of sub- 
stitution, 670. 

Theory, atomic, 213. 

Thermo-electricity, 181. 

Thermometers, 75; construction 
of, 76 ; graduation, 77. 

Thorium, 573. 

Thunder and lightning, 157. 

Tin, 613; alloys of, 614; oxyds 
of, 615; chlorids of, 616; sul- 
phurets of, 617. 

Tissues, waste of the animal, 944. 

Titanium, 612. 

Tolu, balsam, 764. 

Tungsten, 612. 

Turpeth mineral, 645. 

Turpentine, oil of, 821. 

Ulmine, 785. 

Upas, poison of the, 853. 

Uramile, 900. 

Uranite, uranium, 607. 

Urea, 877 ; urine, 925. 

Ure's eudiometer, 395. 

Urinary calculi, 926. 



480 



INDEX. 



Vacuum, 29 ; Torricellian, 33. 

Valerianates, 747. 

Vanadium, 612. 

Vapor of alcohol, density of, 700. 

Vaporization, 115. 

Vapors, maximum density of, 131 ; 
density of determined, 680. 

Vegetable acids, 805. 

Vegetable mould, 785 ; principles, 
858. 

Vegetables, nutrition of, 931 ; tem- 
perature of, 947. 

Veratrine, 855. 

Verdigris, 830. 

Vermillion, 643. 

Vinegar, quick process for, 722. 

Vinic acids, 703. 

Vinous fermentation, 770. 

Viscous fermentation, 772. 

Vital force, 667. 

Vitriol, blue, 610; green, 589; 
oil of, 289 ; white, 600. 

Volatile alkali, 441. 

Volatile oils, 820. 

Voltaic pile, 160; circle, 161,162. 

Voltaism, 158. 

Voltameter, 242. 

Volume, of air, 30 ; combination 
by, 190, 191. 



Water, natural and chemical his- 
tory of, 404; as a chemical 
agent, 408; decomposition of, 
386-390; voltaic, 235; forma- 
tion of, 392, 394 ; unequal ex- 
pansion of, 86. 

Water-hammer, 121. 

Wax, 800. 

Weight and specific gravity, 36. 

White arsenic, 628 ; lead, 728. 

White precipitate, 646. 

Wollaston's goniometer, 229. 

Wood, destructive distillation of, 
787. 

Wood naphtha, 734. 

Wood spirit, 734; oxydation of, 
740 ; ether, 738. 

Woody fibre, 781 ; transformation 
of, 785. 

Xyloidine, 784. 

Yeast, 907 ; action of, 770. 

Yttrium, 573. 

Zaffire, 598. 

Zinc, and oxyd of, 599; acetate 
of, 725; chlorid and sulphuret 
of, 600 ; lactate of, 774 j vale- 
rianate of, 747. 

Zirconium, 573. 



THE END. 



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